NOTIZIARIO Neutroni e Luce di Sincrotrone - Issue 9 n.2, 2004

Rivista del Consiglio Nazionale delle Ricerche

NOTIZIARIO Neutroni e Luce di Sincrotrone

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July 2004 - Aut. Trib. Roma n. 124/96 del 22-03-96 - Sped. Abb. Post. 70% Filiale di Roma - C.N.R. p.le A. Moro 7, 00185 Roma

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Rivista del Consiglio Nazionale delle Ricerche Cover photo: Contour plot and projection of the time-average muon polarisation in silver (I) oxide, Ag2O as a function of applied magnetic field and temperature. From this, detailed information about the muon state electronic structure in this material, can be deduced, informing by analogy on the states adopted by hydrogen.

SUMMARY EDITORIAL

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C.J. Carlile

Twenty-Years Italian/Anglo Science Collaboration to Continue ............................................................................................................................ 3 C. Andreani and R.S. Eccleston

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SCIENTIFIC REVIEWS The Research Scene of Femtosecond X-ray Diffraction.............................................................................................................. 4 P. Bergese and L.E. Depero

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Magnetic Nanostructures studied by polarised neutron reflectometry: recent results and future prospects for polarised reflectometry at ISIS........................... 13

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R.M. Dalgliesh and S. Langridge

Il is published by CNR, and printed in collaboration with the Facoltà di Scienze M.F.N. and the Dipartimento di Fisica of the Neutroni e Luce didegli Sincrotrone Università Studi di Roma “Tor Vergata”.

Vol. 9, N. 2 July 2004 Autorizzazione del Tribunale di Roma n. 124/96 del 22-03-96 DIRECTOR:

C. Andreani

The infrared Beamline SISSI at Elettra

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S. Lupi, A. Nucara, L. Quaroni and P. Calvani

Complex dynamics in polymer electrolytes ............................. 32 A. Triolo, O. Russina, M. Lanza and H. Grimm

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M. Capellas Espuny, G. Cicognani, R.S. Eccleston, D. Herlach, P. King, P. Mikula, A. Schreyer, R. Willumeit

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EDITORIAL

ver the last two years the world of neutron scattering (or at least the European part of it) has been adjusting itself to a new scenario. Up until 2002 it was “business as usual” with Europe’s neutron sources upgrading their facilities incrementally as and when funds were available and the user community was expanding, slowly but surely, and moving into wider scientific areas.

The European Spallation Source was still a realistically attainable dream. The new scenario began to dawn, paradoxically, at the Bonn ESS meeting in the light-filled halls of the new German parliament building, now relieved of its original purpose thanks to a different change of scenario. At this meeting in June 2002 the ESS laid down a challenge to the funding bodies of Europe and relaunched itself. The meeting was a huge success for neutron scattering, enjoyed by all in a festival atmosphere, but not, at least in the short term, for the ESS. It was time for funding bodies to say what they hadn’t wanted to say before. To paraphrase “We do want the ESS, but not now. Instead we should be investing in the world-class sources which we have already and let’s see how the American and the Japanese get along with their big projects before we take the plunge”.

But where was the money to come from to invest in Europe’s current world-leading sources ? Just when science in Europe appeared to be in the doldrums a strange thing happened, at least it appeared strange to normal mortals. In Lisbon at the EU Heads of Governments meeting a pledge was made to turn Europe into “the most dynamic knowledgebased economy in the world by 2010”. And then an even stranger thing happened – a pledge at the next meeting in Barcelona to increase the proportion of European GDP spent on research and development from the 1.8% current average to 3.0% by 2008-2012. A lot of credit for these initiatives must go to Monsieur Philippe Busquin, who has been an excellent European Commissioner for Research, who had earlier launched the grand idea of a European Research Area, and who was quoted as saying last month “No agriculture, but science, education and innovation, are needed to achieve the Lisbon goal”. What can be happening in Europe? Someone speaking the unspeakable – “not agriculture”! The ERA spawned the idea of a European Research Council – initially dismissed by many but now being talked about as having a budget of 10 B over seven years and awarding grants to European researchers on the grounds of excellence only. No juste retour! Neutron scatterers are good at applying for grants so this appears to be a positive move.

The European Strategy Forum on Research Infrastructures created itself just over 2 years ago and its first task was to examine the case for neutrons in general and the ESS in particular. But ESFRI has no direct collective authority for funding, being composed of sets of delegations from the 15 original EU countries and now expanded to 25 plus Switzerland.

Nevertheless its pronouncements carry weight, differing according to whether they are positive or negative. A positive recommendation can be agreed upon by all but there is little means of acting upon it. A negative recommendation however can seriously jeopardise a project. There are signs that DG Research in Brussels wishes this state of affairs to evolve but currently no consensus has been reached.

So the scenario has changed, but how might this affect neu-

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tron scattering in Europe? Firstly, the realization that the ESS will not be funded “tomorrow” means we have had to focus in on our current sources and make the best of the considerable resources which we already have. There are some in Europe who feel we should invest in the SNS as a preparation for ESS. I am not of this opinion. Instead the scarce capital resources which we do have would be better invested in European facilities, in a manner similar to the American policy when the Brookhaven reactor shut down. Whilst specialist neutron scientists in Europe might wish to gain experience on high-power spallation sources there is little risk that the user community as a whole will migrate west (or east).

Therefore we have to invest in our own sources to maintain the health of our considerable user community.

In order to address this question, the ILL, for its part, is reexamining its investment and infrastructure renewal programme – the Millennium Programme – so as to position ourselves better in this new scenario. There are areas where the ILL is pre-eminent and it is these areas upon which we must concentrate. Examples which spring to mind are: where intense beams of cold neutrons are needed as in the case of high resolution spectroscopy; where large focusing monochromators and large position sensitive detectors can be used on instruments such as powder diffractometers; where broad wavelength band beams can be used such as for small angle scattering, neutron spin echo, and single crystal diffractometers employing image plates; where beam reliability and predictability is valued and where beam stability is essential for liquid diffraction for example or for kinetic experiments; where raw intensity is needed including almost all applications involving nuclear physics, or for tomographic imaging. Equally well the employment of polarized neutron techniques – polarized helium-3, polarizing supermirrors, polarizing monochromators (Heuslers), spherical polarimetry (Cryopad), all developed or perfected at ILL – is better suited, experience tells us, to continuous beams.

There are clear signs that our funders – owners and scientific partner nations alike - have recognized this message and are responding. The prospects for further scientific partners in the Institute also look good. The full Europeanisation of the ILL is a necessary step in my view. In these ways, for a relatively small outlay, the 1.5 B capital investment which the ILL represents can be enhanced and optimized in order to help maintain scientific leadership in this field for Europe for the next 15 years at least. The other powerful neutron facilities in Europe will of course also play their part. At that time an operational ESS, complementary to ILL, would be needed. In the meantime we are pleased to announce that the ESS Initiative will relocate to the ILL in order that they maintain a watching brief, enhance the scientific case and launch a bid for funds at an appropriate moment.

We are of course happy to have such an obvious Italian presence at the ILL and indeed at our partner Institutes ESRF and EMBL. We were honoured by the visit of the Italian Senatorial Committee on Science, Education and Culture in May of this year. Such interactions are of mutual benefit and enhance the appreciation of all concerned.

C.J. Carlile Institut Laue Langevin, 6 rue Jules Horowitz 38042 Grenoble Cedex 9 - France

EDITORIAL

TWENTY-YEARS ITALIAN/ANGLO SCIENCE COLLABORATION TO CONTINUE Scientists from the UK and Italy have signed an agreement which builds on a close and very successful collaboration that has lasted for 20 years. Professor Adriano De Maio, president of the Consiglio Nazionale delle Ricerche (CNR - the Italian National Research Council) and Professor John Wood, Chief Executive of CCLRC, signed a Memorandum of Understanding agreeing to collaborate on the development of new technologies and instrumentation.

«The continuing success of this 20-year agreement is very important for us» explained Professor De Maio. «First and most importantly to enable excellent scientific research to take place, but also for many less obvious reasons. Building the neutron instruments at the CNR and on the ISIS facility has enabled great leaps in technical innovation and know-how, increasing industrial competitiveness in the two countries».

Professor Wood was also enthusiastic about the future. «We have to look to the future and coordinate strategy for the new facilities coming on line. We need to make sure new facilities, like the new target station on ISIS - which we’ll start building later this yea - offer complimentary opportunities for scientist, making them stronger and better able to compete with similar facilities outside Europe».

Recent examples of research initiatives that have benefited from this collaboration include investigation on ISIS of candidate hydrogen storage technologies, and Italian archaeological specimens - helping scientists understand how, and from what they were constructed.

Notes for editors Italian scientists have had access to several ISIS instruments over the 20 years, starting with Prisma in 1984, through µSR, EMU, TOSCA, VESUVIO, and looking to the future, NIMROD on ISIS’s second target station which should be available in 2008.

The Italian National Research Council (CNR) is a public organization of great relevance in the field of scientific and technological research of the Country whose original institution goes back to year 1923. It promotes and carry on research activities, in pursuit of excellence and strategic relevance within the national and international ambit, in the frame of European cooperation and integration; in cooperation with the academic research and with other private and public organizations, ensures the dissemination of results inside the Country.

The CCLRC (Council for Central Laboratory of the Research Councils) is a research council. It operates worldleading facilities on its three sites: the Rutherford Appleton Laboratory in Oxfordshire, the Daresbury Laboratory in Cheshire and the Chilbolton Observatory in Hampshire, at which scientists carry out research across a wide range of topics in science and engineering. It is one of Europe’s largest multidisciplinary research organisations supporting scientists and engineers world-wide. It operates world-class large-scale neutron, muon, synchrotron and high-powered laser facilities. Programmes span a wide range of science, engineering, and technology, including: materials science, physics, chemistry, mathematics, life sciences, computer science, particle physics, space science, instrumentation, accelerator-based technologies, IT and e-Science.

C. Andreani & R.S. Eccleston

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Paper received March 2004

THE RESEARCH SCENE OF FEMTOSECOND X-RAY DIFFRACTION Paolo Bergese and Laura E. Depero* INSTM and Structural Chemistry Laboratory, University of Brescia, via Branze, 38, 25123, Brescia (Italy)

If your only instrument is an hammer, you will end up to treat everything as a nail L. M. KRAUSS Femtosecond time-scale phenomena are usually investigated by optical pump/probe experiments. However, this approach does not generally give direct information on the system molecular structure. Time-resolved X-ray diffraction (XRD) is the candidate probe for achieving this target, and opens the study of femtosecond transient structural transformations. Presently, femtosecond time-resolved experiments constitute the cutting-edge of XRD. The successful results of the past five years aroused increasing interest and expectations in the material science community, especially in the perspective of the realization of very-high brilliance X-ray sources, which, in the case of free electron lasers, are expected to reach 1033 photons/(s⋅mrad2⋅mm2⋅0.1%bw) at a wavelength of 0.1 nm. The aim of this paper is to outline recent achievements and ongoing projects in femtosecond X-ray machines and pulse generation, to assess the existing literature, and, finally, to make a tentative census of the groups working on femtosecond XRD and of their main research activities.

Introduction The interaction between a monoenergetic X-ray beam and the electronic distribution of a crystalline material results in a well defined X-ray scattering pattern. The scattering pattern reflects in a macroscopic environment the order of nuclei within the material in terms of both spatial orientation and position. Thus, it is highly sensitive to the material crystal structure and microstructure.

For these reasons, from nearly a century, X-ray diffraction (XRD) is one of the major probes in molecular structure determination and has been used to study the structural and microstructural properties of crystalline (and, to some extent, amorphous) materials. Modern techniques of X-ray production, their interaction with matter and the inherent applications, with special attention to XRD, can be found in a recent monograph by Nielsen and McMorrow [1].

Most of the XRD studies and other X-ray applications

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have been related to steady-state, long-lived systems.

Extension of the X-ray techniques into the time domain can dramatically contribute to the understanding of the mechanisms of formation and transformation occurring in material systems and to make a bridge between their structure and dynamics. Time-resolved XRD is an excellent tool to study the intra- and intermolecular structural changes, and also finds use in a number technological applications, such as lithography. The time resolution of the experiments must cover many orders of magnitude, as the processes themselves have key-times (the time range in which a transient structural intermediate occurs) spanning from tenths of femtoseconds up to kiloseconds.

The conventional way to study the dynamics of ultrafast phenomena is by optical pump/probe experiments.

Such techniques do not directly give the positions of the atoms as a function of time except that in very favourable cases. To the contrary, time-resolved XRD can in principle provide a direct probe for atomic-scale fast dynamic processes, opening the study of transient structural reactions [2].

An ideal time-resolved XRD experiment should have sufficient temporal and spatial resolution to track the sequence of transient events of interest in the observed process. Rapid thermal events, polymorphic phase transitions, and shock-wave propagation occur at a time scale of 10-100 picoseconds. However, to follow vibrations and rotations in single molecules, liquids or crystal lattices, and breaking and formation of chemical bonds, a resolution better than 300 femtoseconds is needed [3].

Moreover, the range of internuclear distances in molecules requires a spatial resolution of approximately 1 Å, which for diffraction requires (hard) X-ray of comparable wavelengths.

Femtosecond time resolution and hard wavelengths (1) are not the only requirements (and difficulties) placed on femtosecond XRD probes. In addition, the X-ray source must have (2) enough brightness, and must be (3) spectrally concentrated and (4) spatially collimated, and (5) synchronized with the (optical laser) pump sources. All of these aspects contribute to the experimental challenges of femtosecond XRD. Indeed, femtosecond (also referred in the literature as ultrafast) X-ray pulses pro-

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duction and application constitute the cutting-edge of time-resolved XRD. Also femtosecond X-ray absorption, being an “unparallel” tool of X-ray diffraction, plays an important role in the study of transient intermediates. Femtosecond X-ray absorption is performed with the same sources of X-ray pulses used in femtosecond XRD. Nevertheless, deeper treatment of the subject is out of the scope of this paper, and exhaustive basics can be found in references [1] and [4]. Other emerging femtosecond time-resolved characterization techniques, not developed here, are X-ray fluorescence [5] and electron diffraction [6].

The natural application of femtosecond XRD is in material science, because this is the time limiting scale on which structural dynamics occur. Investigation of ultrafast dynamic properties of condensed matter systems will facilitate the understanding of phenomena such as bulk and surface melting and dynamics, or dynamic behaviours of grains (nanoscale tribology).

For physical chemists, the direct observation of the molecular structure of the intermediate conformations between reactants and products has been a major goal since the formulation of Eyring’s transition-state theory (1930). The transition states last about 100 femtoseconds, as dictated by the time scale of an atomic vibrational period. Thus, femtosecond XRD opens the possibility to investigate structural properties of molecules during chemical reactions at the kinetics time rate. Examples include organic solids dynamical behaviour, photo-induced order/disorder phenomena in organic conductors, and polymerisation.

In structural biology femtosecond XRD provides the possibility to investigate a class of molecules presently not accessible for structural determination. High brilliance sources will allow to obtain data from these molecules in the very small time window before they are damaged. Using this technique on the smallest creatures capable of self-replication (such as mycoplasmas) it seems possible to observe the processes by which they perform their tasks.

The aim of this paper is to outline recent achievements and ongoing projects in femtosecond X-ray machines and pulse generation, to make a comparative analysis of the existing literature, and, finally, to list the main groups working on femtosecond XRD and their principal research activities. We will concentrate on femtosecond XRD, as it is the actual XRD frontier. An exhaustive monograph on experimental and theoretical aspects of picosecond XRD was edited in 1997 by Helliwell and Rentzepis [7]. Theoretical aspects of interactions between ultrafast X-ray pulses and matter will not be treated here; again some basics can be found in the monograph

by Helliwell and Rentzepis [7] and in the references indicated in Table 1.

Femtosecond X-ray sources Synchrotron methods Synchrotrons have become dramatic tools in X-ray science. These machines accelerate and store relativistic electrons in a ring and use them to emit X-rays from insertion devices and bending magnets. The shortest time resolution which is attainable with the latest (third) generation of synchrotrons is equal or higher than 30 picoseconds [7,8]. Femtosecond time resolution has been the challenge for which novel approaches have been developed.

One of the earliest efforts to generate femtosecond X-rays from relativistic electrons was based on scattering a ultrahigh intensity femtosecond laser pulse with a relativistic electron bunch (Thomson scattering). In this approach, the laser effectively acts as a transient ondulator for the electrons, and under the proper scattering geometry, the duration of the generated X-ray burst is determined by the laser pulse duration. For a detailed description of the Thomson scattering approach in femtosecond X-rays generation, the characteristics of the X-rays, and how they depend on electron and laser beam properties and scattering geometry see the work by Schoenlein et al [9]. The first experiment was realized at Berkeley National Laboratory in 1996 using the existing 20 picoseconds linac with an electron energy of 50 MeV [10]. They succeed to produce about 105 X-ray photons at 0.4 Å and the duration of the X-ray burst was 300 fs. This X-ray flux was high enough to study the ultrafast structural dynamics of crystals (InSb) following femtosecond laser pulse excitation by time-resolved X-ray diffraction [11].

Together with Berkeley, the Thomson scattering approach is presently being pursued at several laboratories in the USA (Brookhaven Natl. Lab. [12] and Thomas Jefferson accelerator facility [9]), and Japan (High Energy Accelerator Res Org, Tsukuba. [13,14]).

An alternative method for generating femtosecond Xrays is to gate them from long-pulse X-ray sources. This approach is feasible with the brightest sources of X-rays presently available, such as the Advanced Light Source (ALS), the Advanced Photon Source (APS), and the European Synchrotron Radiation Facility (ESRF).

The technique uses a femtosecond optical pulse to generate femtosecond X-rays from a storage ring. A femtosecond optical pulse of moderate energy (about 0. 1 mJ) modulates the energy of an ultrashort slice of a stored electron bunch as they propagate through a wiggler. The energy-modulated electron slice spatially separates from the main bunch in a dispersive section of the storage ring and can then be used to generate femtosecond Xrays at a bend-magnet (or insertion-device) beamline.

The original electron bunch is recovered due to synchrotron damping of the electrons in the storage ring. Thus, other synchrotron beamlines are unaffected and special

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operation of the storage ring is not required. For a detailed description of the method see reference [9].

In the context of femtosecond X-ray production, 30 picoseconds synchrotron pulses may be considered as a continuous beam that can be stroboscopically resolved with an appropriate X-ray detector (streak camera) in order to achieve a femtosecond resolution. The detector is equipped with an ultrafast shutter system, whose opening time and frequency must match the time structure of the storage ring as well as the desired timing sequence of the experiment. At the ESRF a complete experimental system with synchronization of a 100–150 femtoseconds laser, synchrotron, rotating chopper and streak camera is now operating. This set up allowed to study the lattice expansion of laser-excited metal nanoparticles [15]. More details on streak cameras technology and experimental methods can be found on the leading paper on the subject published in 1997 by Michael Wulff [16].

The drawback of streak cameras is the low sensitivity (on the order of 0.1%). In combination with the fact that only a small fraction of the X-ray pulse is actually used, this gives a severe limit in the number of detected photons, which can be partially compensated by accumulation. A time resolution lower than 300 femtoseconds may be reached in the forthcoming years for one shot experiments. Developments at ESRF have recently led to an effective time resolution of 460 femtoseconds and 640 femtoseconds, for accumulation times of 1 second (900 shots) and 1 minute (54 000 shots) respectively [8].

Other methods for generating sub-picosecond X-ray pulses from synchrotron have been proposed. The first is based on nonthermal melting of crystals, a reversible transition that occurs below the damage threshold. Nonthermal melting of a Bragg crystal can interrupt X-ray diffraction, which is subsequently reactivated by recrystallization. Then, in principle, by combining two crystals in series and varying the time delay between their melting/recrystallization cycle, a slice of X-ray radiation could be cut [17].

The second approach relies on the scattering of hard Xray photons by a superlattice of optical phonons generated by ultrafast laser pulses incident on a Bragg crystal.

Using a suitable laser system, the crystal lattice motion can be controlled so that efficient Bragg diffraction is switched on and off in a time comparable to a phonon oscillation period (100 – 1000 nanoseconds) [18].

X-ray free-electron laser (XFEL) The free-electron laser (FEL) is a (fourth generation) source for femtosecond X-ray pulses. A strongly bunched and highly intense electron beam is sent through a long ondulator placed after a linear electron accelerator. Under certain challenging conditions selfamplified spontaneous emission (SASE) takes place

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starting from noise. In this way the FEL generates 200 femtoseconds long bunch trains of Fourier-transformlimited and extremely intense spikes with strongly fluctuating intensities. The radiation has the optical properties characteristic of conventional lasers, in particular high spatial coherence. FEL differs from conventional lasers in using a relativistic electron beam as its lasing medium, as opposed to bound atomic or molecular states, hence the term “free-electron”.

The first FEL was built in 1977 at 10 mm radiation wavelength. However, only the idea of SASE opened the path to use a FEL as a source for X-rays. The radiation wavelengths produced by (SASE) FEL currently span from infrared to soft X-rays [19,20] and several projects to extend them to hard X-rays are going on. At the TESLA Test Facility (TTF) of HASYLAB/DESY (Germany), it has been set up the project of a XFEL that generates soft X-ray mrad collimated pulses with 30 femtoseconds of duration, with an average brilliance of 10 22 photons/(s⋅mrad2⋅mm2⋅0.1%bw), with the average number of photons exceeding 1012 photons/pulse [21]. The target XFEL at TESLA is a machine able to generate 100 femtoseconds X-ray collimated beams (few µ rad) as bright as 1033 photons/(s⋅mrad2⋅mm2⋅0.1%bw) at a wavelength of 0.1 nm. This brilliance represents more than ten order of magnitude of what the current synchrotrons can produce with polychromatic 50 picoseconds X-ray bursts [22,23,24]. Another project for the construction of a XFEL, targeted to three spectral bands: the first around 40 nm wavelength, the second around 10 nm and the third in the soft X-ray region (1.5 – 1.2 nm), is underway in Italy at the Synchrotron Light Laboratory ELETTRA [25]. Finally, in Japan, at the SPring-8 Synchrotron Facility, a XFEL (SCSS: SPring-8 Compact SASE Source) is under construction, and hard X-ray (0.1 nm) is the wavelength expected to be achieved in the year 2010 [26].

A worldwide and updated report on FEL researches and projects can be found on the “World Wide Web Virtual Library: Free Electron Laser research and applications” [27], and a Round Table for synchrotron radiation and FEL, funded by the European Commission, exists [28].

Laser-produced plasma (LPP) X-rays The idea to study the laser-plasma X-ray emission was born in the field of laser fusion. The motivation was to study the X-ray emission as it is one of the most rich sources of information for understanding the basic phenomena of laser-plasma interactions. From these experiments it was straightforward to use it on the flip side, i.e. to generate X-rays pulses from laser-produced plasma (LPP).

The energy deposited at the surface of a solid-state target produces a high temperature (500 eV) and dense plasma which remains at near solid densities during the

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interaction because it has no time to expand. In such plasmas, high ionisation stages of ions are reached and strong non-equilibrium states are produced. At laser peak power intensities (around 1000 W / cm 2), strong non-linear processes accelerate some electrons of the plasma to a few tenths of keV. These fast electrons penetrate inside the solid target deeper than the plasma depth and loose their energy mainly by K-shell ionisation of the atoms, which then rearrange emitting monochromatic K X-ray radiation.

Yet in 2000, at LOA of ENTSA (France) the efficiency of the LPP X-ray source was about 109 photons/pulse at a wavelength of about 0.7 nm [29]. Presently, LPP are the most intense, cheap and compact sources of hard X-rays at the time scale of few hundreds of femtoseconds. Indeed, most of the experiments in which femtosecond transient events were tracked by time resolved XRD used this kind of sources (see the next Section).

Recently, soft X-ray bursts produced by the laser-plasma technology touched the attosecond frontier [30,31], such performances have also been theoretically predicted for machines based on synchrotron non-linear Thomson scattering [32] as well as for XFELs [33].

X-ray lasers X-ray lasers are very promising, but at the present stage of development they are still not applicable as routine femtosecond radiation sources. They can be seen as the implementation towards pulsed X-ray production of the conventional laboratory X-ray tubes. Here X-rays are produced as a result of the ionization driven by a femtosecond laser of core level electrons of the atoms of a target This sources display several advantages, including very low costs (if compared with the other femtosecond X-ray sources), compactness (laboratory, tabletop instruments), and manageability (they work at near-room temperature).

More details on X-ray lasers can be found in the works

by Guo et al. [34] and by Egbert et al. [35], and in the references cited in the next section.

Comparative analysis of the literature on femtosecond XRD We conducted a comparative analysis of the published scientific papers concerned with femtosecond XRD. They were searched by the ISI Web of SCIENCE and the resulting list (updated at 24 March 2004 and ordered by the “times cited” criterion) containing the full references and titles of the papers is reported in the Appendix of this work.

Analysis results are summarized in Table 1 and Figure 1.

They were built to stress the subdivision by subject of the papers. In Table 1 each number corresponds to a paper, with reference to the list in the Appendix. Figure 1 is the bubble plot of Table 1: each bubble refers to a re-

search subject, and its area is proportional to the number of papers dealing with that subject.

Table 1 and Figure 1 suggest that most of the papers (both applicative and theoretical) have been focused on the machines and methods for the production of femtosecond X-ray pulses. To date, the major number of applicative experiments with femtosecond XRD probes has been performed in the field of the physics of (condensed) matter, mainly using LPP X-ray sources, and fewer times with synchrotron methods. Whit the same sources also a couple of experiments were realized in physical chemistry, while applications in structural biology are still at the level of theoretical previsions. XFEL machines and related experiments are at the project stage. The hard problem of the detection of femtosecond X-ray pulses is more or less deeply treated in all the papers, especially in the ones dedicated to synchrotron methods (actually, some of them relies on streak camera detectors, see the previous Section). However, a paper dedicated to this specific topic exists.

Finally, it may be noted that the number of review papers (even excluding the present one) exceeds the number of application papers (!). The positive message is that femtosecond XRD is a cutting-edge research field also from the scientific fashion standpoint.

Who does what in the scene of femtosecond X-ray diffraction Femtosecond XRD is a young, frontier research. Femtosecond X-ray sources development is stimulated by experimental applications, and viceversa. Thus, the research groups working on the subject include at their inside both the aspects, instead of focusing on one of them, as usually happens in more mature disciplines. The fol-

Fig. 1. Bubble plot of the subdivision by subject of the scientific papers concerned with femtosecond XRD. Each bubble refers to a research subject, and its area is proportional to the number of papers dealing with that subject. The plot is built on the data of Table 1.

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lowing list, probably far to be complete, includes the main research groups working on femtosecond XRD that we extrapolate by crossing web and scientific papers information.

Ultrafast X-ray machines At HASYLAB/DESY laboratory, in Germany, a (X, XUV)-ray FEL specifically designed to deliver 100 femtoseconds X-ray pulses is under construction [22,23,24].

Projects for the realization of (X, XUV)-ray FELs are also underway in Italy (Synchrotron Light Laboratory ELETTRA [25]) and Japan (SPring-8 Synchrotron Facility [26]).

Studies in synchrotron methods for femtosecond generation of X-ray pulses are going on in USA (Berkeley National Laboratory [9], Brookhaven National Laboratory [12] and Thomas Jefferson accelerator facility [9]), Europe (European Synchrotron Radiation Facility, ESRF) [8], and Japan (High Energy Accelerator Res Org, Tsukuba) [13,14].

LPP (X, XUV)-ray sources are developed in the USA at the Ultrafast structural dynamics of matter laboratories (Scool of Optics/CREOL, Un. of Central Florida) [36]. In Europe it exists an institution that brings together a number of European research groups and institutions who work together to develop and apply (sub)-picosecond LPP X-ray pulses: the TMR Network [37]. The group includes the applied optical laboratories of ENSTA [38] and other academic groups (Jena, Saclay Lund, Essen, Salamanca, Berlin, Pisa Palaiseau-LULI). All the links to

the websites of these groups can be found at the website of the TMR Network [37].

The main groups working on X-ray lasers are the ones that produced the papers indicated by Table 1.

In Europe it is going on a coordinated research project (financed in the frame of the 5th Framework Programme) on femtosecond X-ray sources (FAMTO: ultra-fast atomic movie tools 100 femtosecond time-resolved diffraction installations for the study of ultrafast transient structural changes) [39]. The project is managed by Antoine Rousse of ENSTA. Application of Ultrafast X-rays The groups indicated in the previous Subsection gather the world leaders in femtosecond XRD. Here it follows a list of the group leader researchers and (only) their main applicative interests in femtosecond XRD. Owing to the highly cross-disciplinary nature of the subject and the dimensions of each group these are strong limitations, but necessary for compiling a rough, yet indicative, list.

EUROPE Thomas Tschentscher (HASYLAB/DESY, Ge): (X, XUV)ray Free Electron Laser, femtosecond X-ray LINAC; Richard P. Walker (ELETTRA): (X, XUV)-ray Free Electron Laser; Stephane Sebban, Antoine Rousse (LOA, France): Laser-plasma (X, XUV)-ray sources; Justin Wark (Oxford, GB): theoretical aspects of X-ray diffraction on femtosecond timescales; Jorgen Larsson (LLC/Max-Lab,

Physics of matter

Physical chemistry

Structural biology

Machines

Synchrotron methods

42, 44, 76

7

19, 23, 32, 35, 39, 41, 50, 59, 66, 93

LPP X-rays

1, 2, 3, 4, 9, 12, 13, 34, 37, 38, 78, 85

14

8, 28, 31, 43, 45, 46, 53, 57, 61, 73, 88, 90, 91

X-ray lasers

42

20, 22, 25, 36, 51, 54, 56, 63, 70, 80, 83, 87,89

XFEL Theoretical

64 30, 68

29

5, 11, 27

Reviews

6, 10, 18, 21, 47, 48, 55, 60, 65, 67, 72, 74, 77, 84, 86, 92

Detectors

69

15, 16, 17, 26, 33, 40, 49, 58, 62, 75, 94

Tab. 1. Scientific papers concerned with femtosecond XRD subdivided by the main treated research subject. Each number corresponds to a paper and refers to the list, where the full references and titles of the papers are given, which is reported in this work Appendix. The list was compiled by the ISI Web of SCIENCE‚ and is updated at 24 March 2004.

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Se): Synchronization in ultrafast X-ray experiments; I. Uschmann (Jena, Ge): X-ray optics for femtosecond experiments; Ph. Zeitoun (LIXAM/LOA, Fr): XUV-ray optics for femtosecond experiments; Markus Drescher (bielefeld, Ge): Atomic dynamics with ultrafast XUV radiation; Faris Gelmukhanov (Stockholm, Se): Ultrafast dynamics of relaxation & fragmentation processes; Simone Techert (Göttingen, MaxPlanck, Ge): Applications of ultrafast X-rays in chemistry; Richard Neutze (Göteborg, Se): Ultrafast X-rays in Biology; Michael Wulff (ESRF, Fr): Time-resolved studies of molecular structures and protein crystallography; Klaus Sokolowski-Tinten (Essen, Ge): Solid-(solid, liquid) phase transition; Eric Collet (Rennes, Fr): Photoinduced structural phase transformations; H. Durr (Bessy, Ge): Ultrafast magnetic processes; Janos Hajdu (Uppsala, Sve): time-resolved XRDX in structural biology; H.P. Trommsdroff (Grenoble, Fra): Photochemistry.

AMERICA Robert Schoenlein (Berkeley, USA): femtosecond X-Rays from 3rd generation synchrotron; Stephen Leone (Berkeley, USA): Molecular dynamics with ultrafast XUV radiation; Craig W. Siders (Orlando, USA): Condensed matter structural dynamics; Abraham Szöke (Livermore, USA): Enzymatic reactions in macromolecules; Richard Lee (Berkeley, USA): creating and probing extreme states of matter with ultrafast X-rays; A. Cavalleri (La Jolla, USA): Condensed matter structural dynamics; A.D. Reis (Ann Arbor and Berkeley, USA): Strain propagation.

ASIA Mitsuru Uesaka (Tokio, Japan): Condensed matter structural dynamics; M. Yorozu (Tsukuba, Japan): Generation of femtosecond X-ray pulses by synchrotron radiation; T. Shintake and H. Matsumoto (SPring-8, Japan): (X, XUV)ray Free Electron Laser.

Conclusions Well established static measurement techniques based on X-ray interactions with matter (such as XRD, X- ray microscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy) may be adapted to time-resolved measurements down to the femtosecond time-scale.

However, femtosecond time-resolution has just started to be overcome in XRD. To date, few machines and techniques have been developed for the production and detection of femtosecond (hard and soft) X-ray pulses: in the frame of the synchrotron facilities, in the field of LPP X-rays and by designing laser driven X-ray tubes. A next generation of accelerator-based femtosecond X-ray sources could be the XFELs, which are specifically designed to deliver 100

femtoseconds X-ray pulses with a very-high brillance.

Indeed, 100 femtoseconds and shorter X-ray pulses can now be produced from LPP X-ray systems. These machines have actually been the first to allow the observation of transient events in the femtosecond time-scale with XRD, and have been, to date, the most employed in such experiments. In the future, femtosecond XRD (and other femtosecond time resolved X-ray investigation techniques) will find wide application in a broad and interdisciplinary area of science, including condensed matter physics, chemistry, biology, and engineering. The ability to time-resolve at the femtosecond level could open up entirely new fields of scientific research.

Until today the research has been mainly focused on the designing of femtosecond X-ray sources and on the study of dynamic properties of (crystalline) condensed matter (mainly by monitoring the time evolution of a single Bragg reflection). However, the study of more complex structures is a must. The analysis of more than one Bragg reflecion and the development of ultra brillance sources will be required to reach this goal. Attosecond X-ray pulses production is at the very beginning.

Acknowledgements We grateful acknowledge prof. F. Parmigiani that supported this work in the frame of the INFM-Commissione Luce di Sincrotrone feasibility study: “Science case for a LINAC based VUV X-ray FEL”.

References [1] Nielsen J.A. and McMorrow D., Elements of modern X-ray physics.

Wiley, Chichester, 2001 [2] Rischel C., Rousse A., Uschmann I., Nature, 390, 490-492 (1997) [3] Dohual A., Santamaria J., Eds., Femtochemistry and femtobiology.

World Scientific Publishing, Singapore, 2002 i [4] Nakano H., Goto Y., Lu P., et al., Appl. Phys. Lett. 75, 2350-2352 (1999) [5] Schnurer M., Streli C., Wobrauschek P., et al., Phys. Rev. Lett. 85, 3392-3395 (2000) [6] Cao J., Hao Z., Park H., et al., Appl. Phys. Lett. 83, 1044-1046 (2003) [7] Helliwell JR, Rentzepis PM, Eds., Time-Resolved Diffraction. Oxford Series on Synchrotron Radiation, No. 2. Clarendon Press, New York, 1997.

[8] Rousse A., Rischel C., Gauthier J.C., Cr. Acad. Sci. Iv-Phys. 1: 305-315 (2000) [9] Schoenlein R.W., Chong H.H.W., Glover T.E., et al., Cr. Acad. Sci. IvPhys. 2, 1373-1388 (2001) [10] Schoenlein R.W., Leemans W.P., Chin A.H., et al., Science 274, 236238 (1996) [11] Chin A.H., Schoenlein R.W., Glover T.E., et al., Phys. Rev. Lett. 83, 336-339 (1999) [12] Kashiwagi S., Washio M., Kobuki T., et al., Nucl. Instrum. Meth. A 455, 36-40 (2000) [13] Uesaka M., Kotaki H., Nakajima K., et al., Nucl. Instrum. Meth. A 455, 90-98 (2000) [14] Yorozu M., Yang J., Okada Y., et al., Appl. Phys. B-Lasers O 74, 327331 (2002)

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[15] Plech A., Kurbitz S., Berg K.J., et al., Europhys. Lett. 61, 762-768 (2003) [16] Wulff M., Schotte F., Naylor G., et al., Nucl. Instrum. Meth. A 398, 69-84 (1997) [17] Larsson J., Heimann P.A., Lindenberg A.M., et al., Appl. Phys. AMater. 66, 587-591 (1998) [18] Bucksbaum P.H., Merlin R., Solid State Commun. 111, 535-539 (1999) [19] Schroeder C.B., Pellegrini C., Reiche S., et al., Nucl. Instrum. Meth. A 483, 89-93 (2002) [20] Pellegrini C., Nucl. Instrum. Meth. A 445, 124-127 (2000).

[21] Brefeld W., Faatz B., Feldhaus J., et al., Nucl. Instrum. Meth. A 483, 75-79 (2002) [22] The European X-Ray Laser Project XFEL, http://xfel.desy.de/content/e169/index_eng.html.

[23] Materlik G., Tschentscher T., Eds., The X-ray free electron laser. TESLA technical design report, 2001. Available inside the “The European X-Ray Laser Project XFEL” web site, http://tesla.desy.de/new_pages/TDR_CD/start.html.

[24] TESLA XFEL First Stage of the X-Ray Laser Laboratory Technical Design Report, 2002. Available inside the “The European X-Ray Laser Project XFEL” web site, http://tesla.desy.de/new_pages/tdr_update/start.html.

[25] The FERMI@ELETTRA project, http://www.elettra.trieste.it/projects/index.html.

[26] SPring-8 Compact SASE Source, http://www-xfel.spring8.or.jp/SCSS.htm.

[27] The World Wide Web Virtual Library: Free Electron Laser research and applications, http://sbfel3.ucsb.edu/www/vl_fel.html.

[28] The European Round Table for Synchrotron Radiation and Free Electron Laser, http://www.elettra.trieste.it/roundtable/.

[29] Blome C., Sokolowski-Tinten K., Dietrich C., et al., J. PHYS. IV 11, 491-494 (2001) [30] Drescher M., Hentschel M., Kienberger R., et al., Science 291, 19231927 (2001) [31] Kienberger R., Hentschel M., Spielmann C., et al., Appl. Phys. BLasers O 74, S3-S9 Suppl. S (2002) [32] Lee K, Cha YH, Shin MS, et al., Phys. Rev. E 67, art. no. 026502 Part 2 (2003) [33] Saldin E.L., Schneidmiller E.A., Yurkov M.V., Opt. Commun. 212, 377-390 (2002) [34] Guo T., Spielmann C., Walker B.C., Barty C.P.J., Rev. Sci. Inst., 72, 4147 (2001) [35] Egbert A., Mader B., Tkachenko B., et al., App. Phys. Lett. 81, 23282330 (2002) [36] http://siders.creol.ucf.edu/lab/Research.htm [37] http://www.amolf.nl/research/xuv_physics/tmr_network/ index.html?annual_report99.html [38] http://yvette.ensta.fr/~loa/index_gb.html [39] http://dbs.cordis.lu/cordis-cgi/srchidadb?ACTION=D&SESSION=123782003-523&DOC=2&CALLER=EN_UNIFIEDSRCH&TBL=EN_PROJ&RCN =EP_RCN:52978 or go on the website of CORDIS: http://www.cordis.lu/en/home.html, and search FAMTO.

Appendix In the appendix it is reported the list of the scientific papers concerned with femtosecond XRD, ordered according the “times cited” criterion and updated to 24 March 2004. The Table 1 and the Figure 1 reported in the paper main text are based on this list. The source of the list is the ISI Web of SCIENCE.

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1. C. Rischel, A. Rousse, I. Uschmann et al., Femtosecond time-resolved X-ray diffraction from laser-heated organic films, Nature, 390, 490492 (1997) 2. C. Rose-Petruck, R. Jimenez, T. Guo et al., Picosecond-milliangstrom lattice dynamics measured by ultrafast X-ray diffraction, Nature, 398, 310-312 (1999) 3. A.H. Chin, R.W. Schoenlein, T.E. Glover et al., Ultrafast structural dynamics in InSb probed by time-resolved x-ray diffraction, Phys. Rev. Lett., 83, 336-339 (1999) 4. A. Rousse, C. Rischel, S. Fourmaux et al., Non-thermal melting in semiconductors measured at femtosecond resolution, Nature, 410, 6568 (2001) 5. R. Neutze, R. Wouts, D. van der Spoel et al., Potential for biomolecular imaging with femtosecond X-ray pulses, Nature, 406, 752-757 (2000) 6. D. Umstadter, Review of physics and applications of relativistic plasmas driven by ultra-intense lasers, Phys. Plasmas, 8, 1774-1785 Part 2 (2001) 7. M. Wulff, F. Schotte, G. Naylor et al., Time-resolved structures of macromolecules at the ESRF: Single-pulse Laue diffraction stroboscopic data collection and femtosecond flash photolysis, Nucl. Instrum. Meth. A, 398, 69-84 (1997) 8. C. Reich, P. Gibbon, I. Uschmann et al., Yield optimization and time structure of femtosecond laser plasma K alpha sources, Phys. Rev. Lett., 84, 4846-4849 (2000) 9. A. Cavalleri, C. Toth, C.W. Siders et al., Femtosecond structural dynamics in VO2 during an ultrafast solid-solid phase transition, Phys.

Rev. Lett., 87, art. no.237401 (2000) 10. A. Rousse, C. Rischel, J.C. Gauthier, Colloquium: Femtosecond x-ray crystallography, Rev. Mod. Phys., 73, 17-31 (2001) 11. J.W. Miao, K.O. Hodgson, D. Sayre, An approach to three-dimensional structures of biomolecules by using single-molecule diffraction images, P. Natl. Acad. Sci. USA, 98, 6641-6645 (2001) 12. A. Cavalleri, C.W. Siders, F.L.H. Brown et al., Anharmonic lattice dynamics in germanium measured with ultrafast x-ray diffraction, Phys. Rev. Lett., 85, 586-589 (2000) 13. K. Sokolowski-Tinten, C. Blome, C. Dietrich et al., Femtosecond x-ray measurement of ultrafast melting and large acoustic transients, Phys.

Rev. Lett., 87, art. no. 225701 (2001) 14. M. Bauer, C. Lei, K. Read et al., Direct observation of surface chemistry using ultrafast soft-x-ray pulses, Phys. Rev. Lett., 87, art. no.

025501 (2001) 15. G. Tempea, M. Geissler, M. Schnurer et al., Self-phase-matched high harmonic generation, Phys. Rev. Lett., 84, 4329-4332 (2000) 16. M. BenNun, J.S. Cao, K.R. Wilson, Ultrafast X-ray and electron diffraction: Theoretical considerations, J. Phys. Chem. A, 101, 8743-8761 (1997) 17. T. Missalla, I. Uschmann, E. Forster et al., Monochromatic focusing of subpicosecond x-ray pulses in the keV range, Rev. Sci. Instrum., 70, 1288-1299 (1999) 18. R. Neutze, J. Hajdu, Femtosecond time resolution in x-ray diffraction experiments, P. Natl. Acad. Sci. USA, 94, 5651-5655 (1997) 19. M.F. DeCamp, D.A. Reis, P.H. Bucksbaum et al., Coherent control of pulsed X-ray beams, Nature, 413, 825-828 (2001) 20. T. Guo, C. Spielmann, B.C. Walker et al., Generation of hard x rays by ultrafast terawatt lasers, Rev. Sci. Instrum., 72, 41-47 Part 1 (2001) 21. J. Wark, Time-resolved X-ray diffraction, Contemp. Phys., 37, 205-218 (1996) 22. Y. Fujimoto, Y. Hironaka, K.G. Nakamura et al., Spectroscopy of hard X-rays (2-15 keV) generated by focusing femtosecond laser on metal targets, Jpn. J. Appl. Phys. 1, 38, 6754-6756 (1999) 23. M. Uesaka, T. Watanabe, T. Ueda et al., Production and utilization of

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Lett., 79, 4506-4508 (2001) 47. D. von der Linde, K. Sokolowski-Tinten, C. Blome et al., Generation and application of ultrashort X-ray pulses, Laser Part. Beams., 19, 1522 (2001) 48. J.C. Kieffer, C.Y. Chien, F. Dorchies et al., Ultrafast laser-based thermal X-ray sources, CR. Acad. Sci. IV-Phys., 1, 297-303 (2000) 49. P.H. Bucksbaum, R. Merlin, The phonon Bragg switch: a proposal to generate sub-picosecond X-ray pulses, Solid State Commun. 111, 535539 (1999) 50. R. Neutze, R. Wouts, Deconvoluting ultrafast structural dynamics: temporal resolution beyond the pulse length of synchrotron radiation, J. Synchrotron. Radiat., 7, 22-26 Part 1 (2000) 51. Y. Hironaka, Y. Fujimoto, K.G. Nakamura et al., Enhancement of hard x-ray emission from a copper target by multiple shots of femtosecond laser pulses, Appl. Phys. Lett., 74, 1645-1647 (1999) 52. S. Tanaka, S. Mukamel, Probing exciton dynamics using Raman resonances in femtosecond x-ray four-wave mixing, Phys. Rev. A, 67, art. no.033818 (2003) 53. M. Chen, J.W. Chen, H.Y. Gao et al., Characteristics of ultrafast K line hard x-ray source from femtosecond terawatt laser-produced plasma, Chinese Phys., 12, 55-59 (2003) 54. Y. Jiang, T. Lee, C.G. Rose-Petruck, Generation of ultrashort hard-xray pulses with tabletop laser systems at a 2-kHz repetition rate, J. Opt. Soc. Am. B, 20, 229-237 (2003) 55. J.C. Gauthier, A. Rousse, New sources of ultrashort pulse X-ray radiation and applications, J. Phys. IV, 12, 59-67 (2002) 56. A. Egbert, B. Mader, B. Tkachenko et al., High-repetition rate femtosecond laser-driven hard-x-ray source, Appl. Phys. Lett., 81, 23282330 (2002) 57. C. Ziener, I. Uschmann, G. Stobrawa et al., Optimization of K alpha bursts for photon energies between 1.7 and 7 keV produced by femtosecond-laser-produced plasmas of different scale length, Phys. Rev. E, 65, art. no.066411 Part 2 (2002) 58. D. Salzmann, C. Reich, I. Uschmann et al., Theory of K alpha generation by femtosecond laser-produced hot electrons in thin foils, Phys.

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68. B.W. Adams, Time-dependent Takagi-Taupin eikonal theory of X-ray diffraction in rapidly changing crystal structures, Acta Crystallogr. A, 60, 120-133 Part 2 (2004) 69. K. Oguri, T. Ozaki, T. Nishikawa et al., Femtosecond-resolution measurement of soft-X-ray pulse duration using ultra-fast population increase of singly charged ions induced by optical-field ionisation, Appl. Phys. B-Lasers O, 78, 157-163 (2004) 70. M. Hagedorn, J. Kutzner, G. Tsilimis et al., High-repetition-rate hard X-ray generation with sub-millijoule femtosecond laser pulses, Appl.

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Front. C Tec., 13, 161-170 (2003) 72. K. Hatanaka, T. Miura, H. Odaka et al., Various methods for X-ray pulse generation using a femtosecond laser and their potential for time-resolved X-ray analyses, Bunseki Kagaku, 52, 373-381 (2003) 73. G. Pretzler, F. Brandl, J. Stein et al., High-intensity regime of x-ray generation from relativistic laser plasmas, Appl. Phys. Lett., 82, 36233625 (2003) 74. D. von der Linde, K. Sokolowski-Tinten, X-ray diffraction experiments with femtosecond time resolution, J. Mod. Optic., 50, 683-694 (2003) 75. D. Boschetto, C. Rischel, I. Uschmann et al., Large-angle convergentbeam setup for femtosecond X-ray crystallography, J. Appl. Crystallogr., 36, 348-349 Part 2 (2003) 76. A. Plech, S. Kurbitz, K.J. Berg et al., Time-resolved X-ray diffraction on laser-excited metal nanoparticles, Europhys. Lett., 61, 762-768 (2003) 77. G.K. Shenoy, Impact of next-generation synchrotron radiation sources on materials research, Nucl. Instrum. Meth. B, 199, 1-9 (2003) 78. A. Cavalleri, C. Blome, P. Forget et al., Femtosecond X-ray studies of photoinduced structural phase transitions, Phase. Transit., 75, 769-777 Part B (2002) 79. H. Kishimura, A. Yazaki, H. Kawano et al., Picosecond structural dynamics in photoexcited Si probed by time-resolved x-ray diffraction, J. Chem. Phys., 117, 10239-10243 (2002) 80. K. Kondo, M. Mori, T. Shiraishi, X-ray generation from fs laser heated Xe clusters, Appl. Surf. Sci., 197, 138-144 (2002) 81. Y. Okano, H. Kishimura, Y. Hironaka et al., X-ray and fast ion generation from metal targets by femtosecond laser irradiation, Appl. Surf.

Sci., 197, 281-284 (2002) 82. Y. Hironaka, A. Yazaki, H. Kishimura et al., Picosecond X-ray diffraction from laser-irradiated crystals, Appl. Surf. Sci., 197, 289-293 (2002) 83. A. Egbert, B.N. Chichkov, C. Fallnich et al., Femtosecond laser-driven x-ray tube, Opt. Eng., 41, 2658-2667 (2002) 84. P. Coppens, I.V. Novozhilova, Introductory Lecture - Time-resolved chemistry at atomic resolution, Faraday Discuss., 122, 1-11 (2003) 85. O. Synnergren, M. Harbst, T. Missalla et al., Projecting picosecond lattice dynamics through x-ray topography, Appl. Phys. Lett., 80, 37273729 (2002) 86. B.W. Adams, Manipulation and detection of x rays on the femtosecond time scale (invited), Rev. Sci. Instrum., 73, 1632-1636 Part 2 (2002) 87. A. Egbert, B. Mader, B.N. Chichkov, Novel femtosecond laser-driven X-ray source, Laser. Phys., 12, 403-408 (2002) 88. A. Rousse, C. Rischel, S. Fourmaux et al., Time-resolved femtosecond x-ray diffraction by an ultra-short pulse produced by a laser, Meas.

Sci. Technol., 12, 1841-1846 (2001) 89. A. Egbert, B.N. Chichkov, A. Ostendorf, Ultrashort X-ray source driven by femtosecond laser pulses, Europhys. Lett., 56, 228-233 (2001) 90. N. Uesugi, H. Nakano, T. Nishikawa et al., Efficient soft X-ray generation from femtosecond-laser-produced plasma and its application to time resolved spectroscopy, J. Phys. IV, 11, 397-403 (2001)

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91. C. Blome, K. Sokolowski-Tinten, C. Dietrich et al., Set-up for ultrafast time-resolved X-ray diffraction using a femtosecond laser-plasma keV X-ray source, J. Phys. IV, 11, 491-494 (2001) 92. M. Jacoby, Femtosecond X-ray diffraction, Chem. Eng. News., 75, 5-5 (1997) 93. R.W. Schoenlein, A.H. Chin, H.H.W. Chong, R.W. Falcone, T.E. Glover, P.A. Heimann, S.L. Johnson, A.M. Lindenberg, C.V. Shank, A.A. Zholents, M.S. Zolotorev, Ultrafast X-ray science at the advanced light source, Synchrotron Radiation News, 14, 20-27 (2001) 94. X. Lu, Y.J. Li, Y. Cang et al., Simulation study of a Ne-like Ti x-ray laser at 32.6 nm driven by femtosecond laser pulses, Phys. Rev. A 67, Art. No.013810 (2003)

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Paper received October 2003

MAGNETIC NANOSTRUCTURES STUDIED BY POLARISED NEUTRON REFLECTOMETRY: RECENT RESULTS AND FUTURE PROSPECTS FOR POLARISED REFLECTOMETRY AT ISIS R.M. Dalgliesh and S. Langridge

Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, United Kingdom

Recent developments in the fabrication of artificial magnetic nanostructures have led to a new insight in magnetism in systems which have reduced thickness (relative to the magnetic exchange length) or symmetry breaking surfaces and interfaces. The physics of such systems is of fundamental interest and has also led to significant device applications. Polarised Neutron Reflectometry (PNR) provides absolute depth dependent vector magnetometry information coupled with a structural characterisation. Moreover, in-plane magnetic structures can be studied. In this article we shall review a selection of the recent investigations using polarised neutron reflectometry at ISIS, the resulting physical insight and the future instrumentation and possibilities for magnetic nanostructure research.

probes such as resonant magnetic x-ray reflectometry, XPEEM (x-ray polarised electron emission microscopy), magnetic circular dichroism has provided enormous insight into the magnetism of thin film systems.

1. General Introduction In recent years, the study of solid state magnetism has undergone a revolution in the area of magnetic nanostructures. This has been jointly driven by the discovery of the giant magnetoresistance effect (GMR) in 1988 and the development of advanced deposition techniques such as sputtering and molecular beam epitaxy (MBE). It is now possible to grow magnetic multilayers with atomic-plane precision, potentially with tailor-made physical properties. In parallel, the transition from scientific discovery to commercial exploitation has been dramatic in this field, a panoply of practical applications exist including magnetic devices for data storage, many types of sensor and, potentially, quantum computing. As will be outlined in the following discussion, polarised neutron reflectometry is ideally suited to the study of such systems. a. Introductory Ideas It was realised that the development of Polarised Neutron Reflectometry (PNR) in the 1980’s would provide an extremely powerful technique in the study of thin film systems. The pioneering work of Felcher and co-workers [1] rapidly developed and there was an increasing realisation that PNR is an experimental realisation of an absolute in-plane vector magnetometer [2,3]. In parallel, by combining PNR with more conventional techniques such as magnetometry (SQUID, VSM, MOKE etc.), ferromagnetic resonance, x-ray reflectometry and spectroscopic

Basic Formalism Here we shall only present a rudimentary description of the underlying theory of the PNR technique. For a more detailed description the reader is directed towards reference 2. For wider ranging reports of the application of the PNR technique the reader is directed to the excellent recent reviews [4,5].

As in conventional optics we can define a scattering potential that the neutron experiences in a medium. For a neutron incident on such a medium the scattering potential contains both a nuclear (VN) and a magnetic potential (VM) component: V = VN + VM =

2πh2 Nb - î • B mn

(1)

where mn is the mass of the neutron, N is the number density in the medium, b is the coherent scattering length, µ is the neutron magnetic moment and B is the magnetic induction in the medium. Substituting this potential into the Schrödinger equation a solution may be found that allows an exact calculation of the spin-dependent reflectivity from a sample consisting of discrete layers. Each layer may be described, in the simplest case, by a thickness, average scattering length and an absolute vector magnetic moment. This is analogous to the case for optical light reflection where matrix methods also allow the exact calculation of the reflected and transmitted intensities. The solution of the wave equation within these layers using a matrix approach [2] then allows the spin dependent reflectivity to be calculated for noncollinear magnetic structures as a function of the measured wavevector transfer, QZ: Qz =

4π sin θ λ

(2)

where θ is the angle of reflection and λ is the incident neutron wavelength. An analysis of the polarisation state

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of the reflected neutrons (longitudinal polarisation analysis) allows the spin flip (SF) and the non spin flip (NSF) contributions to be separated. For the typical experimental geometry presented in Figure 1, the components of the in-plane magnetisation, M parallel to the quantisation axis will not change the spin state of the incident neutron upon reflection, whereas, components orthogonal to this axis will give rise to SF scattering. Such an analysis then allows the determination of the in-plane mangetisation. b. The CRISP Time of Flight Reflectometer The CRISP reflectometer is a time of flight polarised neutron reflectometer which views a liquid Hydrogen moderator at a temperature of ~23K. The details of the CRISP reflectometer can be found in references 6,7. Briefly, CRISP (See Figure 2) is a vertical scattering geometry instrument which views a neutron wavelength band of 0.5Å-6.5Å as selected by a wavelength selecting disk chopper operating at 50Hz. Background suppression is via a Nimonic chopper. The unpolarised incident beam is polarised through reflection from an FeCoV/TiN remanent polariser [7], with an increased lower wavelength cut off of 1.2Å and the spin controlled by a non-adiabatic spin flipper. A 30Oe guide field maintains the neutron polarisation pre and post sample. Polarisation analysis

Fig. 1. The scattering geometry typically employed in PNR measurements. The incident neutron beam is polarised in the ±y-direction (parallel to H). Components of the vector magnetisation M parallel to the neutron quantisation axis will give rise to non-spin flip scattering (NSF).

Components of M orthogonal to this produce spin flip (SF) scattering.

may be achieved by an equivalent flipper, analyser assembly. In the case of a diffusely scattered beam an analysing mirror assembly can be installed. Given the incident wavelength range, a typical reflectivity profile can be achieved in 2-3 angular settings of the reflectometer (see Eqn. 2). Furthermore, the wavevector resolution is

Fig. 2. A schematic of the CRISP polarised neutron time of flight reflectometer. The neutron beam is incident from the right at an inclination of 1.5° to the horizontal

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constant in ∆Q/Q and is dominated by the incident collimation (defined by the beam defining slit geometry) and is typically of order 2-4% (∆Q/Q). Flexible sample environment equipment is available covering the field range up to 1.6T and temperatures from 2K up to 200°C. 2. Specular Reflectivity As previously described, PNR may be considered as a technique which provides an absolute vector magnetisation profile of the system under investigation. Moreover, simultaneously, the physical structure of the system is obtained. In the case of the specular reflection of neutrons (incident angle equal to the reflected angle) there is no momentum transfer into the plane of the sample and so information is provided on the structure (both nuclear and magnetic) parallel to the surface normal. This is ideally matched to the magnetic nanostructures discussed in section 1. By way of example we shall consider three topical areas of research.

a. Exchange Coupling The revolutionary development in applications is the creation of devices that exploit the spin rather than the charge of the electron. It is now well known that magnetically coupled multi-layers consisting of 3d ferromagnetic layers interleaved with non-magnetic spacers exhibit giant magnetoresistance (GMR) [8] for appropriate thicknesses of the non-magnetic spacer layer. These are the regimes in which the oscillatory interlayer coupling has an antiferromagnetic ground state between the ferromagnetic layers. The oscillation in coupling with spacer thickness is due to the quantum interference of spin-polarised wave functions[9]. The observed change in resistivity results from the spin dependent scattering of the conduction electrons which depends not only on the magnetic moment alignment but also on the interfacial disorder [10]. One such device made of magnetic multilayers, called a spin valve, is already employed as a read head for computer hard disks, and this has led to dra-

Fig. 3. (a) The observed magnetoresistance of the Co/Cu multilayer described in the text. The submonolayer damage has a dramatic effect on the transport but is not observable through characterisation techniques such as x-ray reflectometry etc. (b) The room temperature magnetisation as measured by the magneto-optic Kerr effect. (c) The polarised neutron reflectivity. The solid lines are fits to the data as visualised in panel (d).

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matic improvements in data storage densities. Arrays of spin valves may also be used to create magnetic random access memory, which has the advantage of being nonvolatile, yet faster, higher density and lower cost than the current dynamic random access memory devices.

Of particular interest is the magnetic coupling in GMR systems and its role in the magnitude of the observed GMR particularly in the case of in-plane disorder. Marrows et al. [11] observed that sub-monolayer damage of a multilayer stack could significantly influence the observed GMR. Typical transport data for Co/Cu multilayer is shown in Figure 3(a,b). For the clean sample there is a large GMR and a zero remanence magnetisation curve. By introducing residual gas damage, the GMR is significantly reduced and a remanence of √2/2* MSAT is developed, where MSAT is the saturation magnetisation.

Such data is indicative of an additional biquadratic term in the exchange coupling giving rise to a non-collinear alignment of the Co magnetisation. The PNR data from the gas damaged multilayer [Co(10 Å)/Cu(9Å)] 25 is shown in Figure 3c. There are several features of interest.

The first order Bragg peak at Q=0.33Å-1 corresponds to

the structural periodicity of the multilayer and magnetic information for which the magnetic propagation vector is 0 i.e. ferromagnetism. At half of this wave-vector is a further Bragg peak which arises solely from the antiferromagnetic correlations between the Co layers. The strong splitting of the two reflectivity curves for the two ↑ ↓ neutron spin states (R , R ) , is visible close to the critical edge (and at the first order Bragg peak). This is indicative of ferromagnetic coupling and a single domain state sample. To understand such a system a fully dynamical analysis [12] approach is employed which reproduces all of the features in Figure 3c and is visualised in panel (d).

To constrain the resulting model it is important to make use of complementary measurements. Conventional xray reflectometry is used to refine the physical structure of the multilayer (fitted simultaneously with the neutron data). By saturating the sample, the magnetic structure is simplified and a measurement of the PNR can extract absolute moment determinations. To obtain the resultant model it is then simply necessary to relax the in-plane orientation of the magnetic structure. The resulting biquadratic structure resolves the apparent contradiction

Fig. 4. (a) A MOKE loop for a naturally exchange biased system (Fe/IrMn). (b) An idealised schematic of the antiferromagnet-ferromagnet interface.

Fig. 5. (Top panel) Spin analysed polarised neutron reflectivity from the double superlattice described in the text. SF and NSF antiferromagnetic correlations are clearly visible for the domain wall phase. (Lower panel) A schematic of the domain wall structure residing in the antiferromagnet.

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Fig. 6. The spin asymmetry for (a) 1500Å and (b) 3000Å Pb film. The Keissig fringes from the thick layer are clearly visible. The solid lines are the fits for the flux exclusion in the layers.

of the existence of ferromagnetism and antiferromagnetic coupling [13]. The physical origin of the biquadratic coupling is described by the well-known Slonczewski coupling fluctuation model of biquadratic exchange [14] where different lateral regions of the multilayer (as imposed by the sub-monolayer damage) have positive and negative exchange coupling. b. Exchange Bias Exchange bias results from the exchange interaction between an antiferromagnet and a ferromagnet. The experimental manifestation is that the magnetisation loop is no longer centred around zero magnetic field (satisfying time reversal symmetry) but is offset from zero magnetic field i.e. a uni-axial anisotropy by an amount known as the exchange bias field, HE (see Figure 4). The effect was first observed by Meiklejohn and Bean in 1956 in a CoCoO granular system [15]. Despite being the method of magnetically pinning the reference layer in technologically important devices such as spin valves [16] the mechanism is not fully understood. Simple models significantly overestimate the magnitude of the exchange bias and do not describe the enhanced coercivity, which is experimentally observed in exchange biased systems or the bias’ temperature dependence. A partial explanation for the lack of understanding is the difficulty in characterising the buried interface between the antiferromagnet and ferromagnet. In this respect, the layer dependence of scattering techniques is advantageous. To

gain a further insight into these phenomena the ability to artificially engineer systems has been exploited in socalled double superlattices [17]. The sign of the exchange coupling can be controlled through the production of an antiferromagnetically coupled multilayer ferromagnetically coupled to a ferromagnetically coupled multilayer.

Such a system will be a suitable model for a very smooth AF/FM interface with near perfect coupling where layers of Co represent layers of atomic spins in a real system. Given the ideal nature of the interface, it is a good system in which to test models of the exchange bias. Two theories have been proposed to describe the observed exchange bias based on domain models either perpendicular or parallel to the interface. Malozemoff [18] proposed that roughness at the interface creates a random exchange field, which depending on the anisotropy in the antiferromagnet may favour the formation of perpendicular domain walls in the AF. Alternatively, Mauri and co-workers [19] proposed that even at a smooth interface the bias could be generated by the formation of parallel domain walls in the antiferromagnet. The spin engineered double superlattice allows this later model to be tested. Steadman and co-workers produced double superlattices of Co/Ru with the nominal structure Si(001)/Ta(75Å)/[Co(35Å)/Ru(15 Å)]9Co(35Å)/Ru(15 Å) [Co(60Å)/Ru(10 Å)]10Ta(75 Å) [20]. Such dc magnetron sputtered systems have a low structural roughness of ~2Å. To identify the proposed domain wall model polarisation analysis provides valuable additional information on the layer dependent in-plane orientation. The polarised neutron reflectivity with polarisation analysis is shown in Figure 5. Three Bragg peaks are clearly observable corresponding to the antiferromagnetic ordering (QAF~0.054Å-1), the structural (magnetic) Bragg peak associated with the ferromagnetic bock (QStruct+FM~0.091Å-1) and the the structural (magnetic) Bragg peak associated with the antiferromagnetic bock (QStruct+AF~0.108Å-1). The polarisation analysis allows a separation of the parallel and orthognonal components (relative to the neutron quantisation axis) of the layer magnetisation. Upon the reduction of the applied magnetic field from saturation the antiferromagnet exhibits a spin flop phase and then winds in to the parallel domain wall (see Figure 5) as predicted by Mauri well over a decade before. The results illustrated the requirement to have anisotropy in the antiferromagnet and that the domain wall is primarily confined to the antiferromagnetic superlattice. c. Magnetism and Superconductivity The interplay between magnetism and superconductivity has generated enormous interest given the mutual exclusivity of the two phenomena. Artificial magnetic nanostructures allow one to study in a systematic manner the proximity effect between a superconductor and a

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ferromagnet. PNR is able to provide information on both the flux penetration and the magnetic structure. The coexistence of 3D superconductivity and magnetism has recently been discovered at ISIS [21]. The superconducting ordering temperature of blocks much thinner than the coherence length is comparable to the bulk for an antiferromagnetic alignment of ferromagnetic blocks, but the superconductivity is suppressed when the orientation is ferromagnetic, suggesting new possibilities to study the interplay between these usually mutually exclusive phenomena and the potential for a superconducting spin valve. Until recently, the thickness of the superconducting layer has been sufficient to suppress the coherent propagation of the magnetic ordering. Recently, Deen and co-workers have studied single crystal Gd/La superlattices [22] in which the Gd layers couple ferromagnetically across the superconducting La layers.

For conventional rare-earth superlattices the magnetic coupling is mediated by a spin density wave. The opening up of a superconducting gap in the La layers does not effect the magnetic ordering. It is hoped that such studies will provide a new insight into interaction between magnetism and superconductivity.

In the case of purely superconducting systems a knowledge of the magnetic induction profile at the surface of a superconductor allows one to test ideas in the GinzburgLandau theory. PNR has been demonstrated to provide valuable information on such parameters as the penetra-

tion depth [23], which are less readily accessible through other techniques. Furthermore, PNR has been used to study magnetic vortices, which form in type-II superconductors [24]. The current transport in such systems, which is crucial to technological applications (high field magnets, field sensors, novel spin-valves etc.), depends on the pinning of such vortices. Reducing the size of such systems results in significantly different behaviour to that of the bulk. By varying the film thickness of the superconducting layer (for thicknesses comparable to the penetration length) the energy benefit of forming a normal vortex core against the energy loss from the surface flux expulsion. As PNR is sensitive to the magnetic induction, B, such flux expulsion and vortices should be observable. Lee and co-workers [25] have investigated this energy balance in thin Pb films deposited by dc magnetron sputtering. Detailed measurements of the spin asymmetry: Θ=

(R (R

↑

− R↓

↑

↓

+R

) )

(3)

below the transition temperature (T=3K, TC~6K) give information on the spatial variation of the magnetic flux density within the Pb layer. The results are presented in Figures 6,7. In the thicker sample, the analysis clearly indicates the presence of a vortex structure. Such observations will allow comparison with both the theory of

Fig. 7. A schematic view of the flux density profile in the superconducting phase resulting from the previous modelling for the two film thicknesses. The vortex structure is clearly visible in the centre of the Pb film.

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Fig. 8. A schematic reciprocal space map showing some of the common features observed in off-specular neutron reflection.

mesoscopic superconductivity and with more complicated magnetic-superconducting systems.

3. Offspecular scattering Diffuse scatter observed around the specularly reflected beam is known as off-specular reflection or scattering.

Structure in this scatter may be related to in-plane correlations within the interface under investigation in the di-

Fig. 9. Reciprocal space maps of off-specular reflectivity from a disordered [Co/Cu] multilayer. (a) in remnant field of 40Oe and (b) in a saturating field of several kOe.

rection parallel to the incident beam. A number of features that are frequently observed are illustrated in Figure 8. These include the so called "Yoneda Wings", diffraction peaks and streaks of intensity at constant Qz. The origins of the these types of scattering are broadly understood but the subtle nuances that enable a detailed understanding and description of any particular problem are still a matter of continuing theoretical and experimental development [26,27].

A number of theoretical treatments of off-specular reflectivity from distinct types of interface exist; these include self-affine fractals, islands, pitted surfaces and capillary waves but all theses analyses are based, in general, on the use of the Distorted Born Wave Approximation (DWBA). A description of these theoretical treatments will not be undertaken here and the reader is directed to a series of detailed texts describing both the derivation and experimental application of these techniques in references 28, 29, 30, 31, 32. In a number of the cases mention above the evaluation of non-analytical integrals is required making calculation computationally expensive.

Fortunately a number of approximations are possible [28], in particular where the scattering occurs at Q vectors well away from the critical edge. It is clear that the future increasing demands will require the development of more advanced analysis techniques.

In recent years off-specular scattering has been studied in order to increase our understanding of a number of different magnetic systems. The ever-decreasing grain sizes required to increase storage density in recording media has generated particular interest. The highest densities of today are approaching the limits of thermal stability and, as a consequence, patterned nanoparticle assemblies are being considered for data storage. Multilayers also offer a new approach to some of the canonical problems in condensed matter research, such as the interplay between superconductivity and magnetism, and

Fig. 10. Schematic diagrams of "Magnetic Roughness" (a) A structurally rough, single domain state. (b) An atomically smooth interface with a domain structure. (c) A system combining

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Fig. 11. Reciprocal space maps of the off-specular reflectivity from an [Fe(3.0nm)/Cr(1.0nm)] multilayer (Top panel) as deposited with no annealing (Lower panel) after 7 hours annealing at 723K.

quantum confinement within thin layers. The ability of neutrons to probe buried interfaces and their sensitivity to magnetic structure means that they are ideally suited this type of problem.

In order to better understand the underlying physics behind this industrial driving force, numerous groups have begun to investigate model multilayer systems. Figure 9 shows two reciprocal space maps calculated from a time of flight spectrum obtained by Langridge et al. from such a model film. In this case the film is a Co/Cu multilayer, figure 9 (a) shows the off-specular reflectivity at a low applied field (~40Oe) and 8(b) the reflectivity at a saturating field of 700 Oe. The specular ridge is clearly visible in both cases, running horizontally at Qx=0.0.

Two Bragg peaks are visible at low applied field, one due to the periodic structure of the multilayer and the other an anti-ferromagnetic ordering peak. Diffuse scattering associated with the AF peak is also observed at

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low field. This scattering may be "switched off" by applying a saturating field to the sample and so must be associated with some sort of magnetic structure. Figure 10 illustrates a number of possible magnetic structures at the interfaces between layers that would result in magnetic off-specular scattering. Langridge et al. [33] considered such distributions of domains and have developed a framework within which the off-specular scattering from around a Bragg peak, such as those shown, may be fitted to extract a correlation length that characterises the magnetic domain disorder within a multilayer. For this case a systematic study of the field dependence of the scattering around the AF ordering peak revealed a large domain disorder in the Co layers close to the coercive field. As the applied field strength was increased the domain sizes increased, the disorder in the magnetisation direction of the domains reduced as the moments aligned along the applied field direction and the antiparallel alignment across the non-magnetic Cu spacer was reduced. The strong field dependence of the domain disorder and size along with the changes in interlayer coupling reveal the close relationship between interfacial structure and the GMR effect.

Takeda et al have also investigated the effect of interfacial roughness on the GMR effect by producing Fe/Cr multilayers within which the interfacial roughness has been systematically varied by annealing. Figure 11 (a) shows a Qx-Qz (cf. Figure 1) map of the reflected intensity from an unannealed film of [Fe(3.0nm)/Cr(1.0nm)].

Two Bragg peaks are visible at Qz=0.8Ă…-1 and Qz=1.6Ă…-1 these correspond to the antiferromagnetic ordering and the bilayer structure. The bright streak of intensity around the antiferromagnetic ordering peak indicates that strong magnetic roughness correlations exist between the layers Figure 11 (b) shows the result of annealing a twin film at 723K for 6 hours. It can be seen that in addition to the scatter around the antiferromagnetic peak a streak of intensity now also appears around the structural Bragg peak indicating that the interlayer correlations have been enhanced. Both off-specular and specular data have been fitted for these samples and from these fits magnetic and structural interfacial roughness parameters calculated. Takeda et al have concluded that, in this case, large in-plane correlation lengths have no beneficial effect on the GMR effect within the films.

However, an understanding of the nature of the magnetic interfacial roughness was not achieved in these experiments and so further work investigating the spin dependence of the off-specular scattering has been undertaken. Initial results have shown that the magnetic scattering is dominated by the spin-flip components indicating that the magnetic moments with the films are aligned with a significant component perpendicular to the applied field.

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Patterned Multilayers Current lithographic techniques could potentially allow increases in storage densities up to terrabits/in2, hence an understanding of the effect of patterning on the magnetic structure of candidate materials on the micron scale is crucial. As part of a program to investigate the effect of such physical patterning on the magnetic behaviour of thin films, the effect of stencilled ion irradiation on a Co/Pt multilayer has been studied by Telling et al.

[34,35]. Argon ion bombardment using a grid to mask regions of a film was anticipated to produce a structure within which the non-irradiated areas would have magnetic moments rotated out of the plane of the film while in irradiated areas the magnetic moment would lie in the plane. A striped array of magnetic moments perpendicular and parallel to the neutron polarisation direction could therefore be obtained resulting in a magnetic diffraction grating the periodicity of which could be measured directly using off-specular reflection. Subsequent application of a saturating magnetic field would destroy

the anisotropy direction. The long-term aim of this work is to characterise the artificially induced periodicity and the nature of the magnetic behaviour under the influence of an external field.

Fig. 12. The integrated intensity around the specular reflection from a patterned Co/Pt multilayer, showing diffraction peaks from a "Magnetic Grating" (indicated by arrows) at low and high field.

Fig. 13. Angle vs. wavelength plots of the spin dependent reflectivity from an iron nonoparticle assembly embedded in a zirconia matrix.

this magnetic periodicity showing that the desired longrange magnetic periodicity had been achieved. Figure 12 shows the scattered intensity measured around the specular peak integrated across all wavelengths. Two diffraction peaks either side of the specular ridge are clearly visible at a remnant field of 40 Oe. The positions of the peaks correspond well with the anticipated position calculated from the known 13Âľm periodicity of the stencil grid. At a saturating field of 3kOe the peaks have clearly disappeared indicating that the anticipated structure with long-range magnetic order had been achieved rather than a structurally patterned film.

Further, more recent, measurements have investigated samples where ion implantation has been used to produce non-magnetic regions in a film rather than rotating

low the surface and that the calculated model value agreed quantitatively with the experimentally determined magnetisation. Further more detailed examination of the off-specular scattering from the sample has revealed magnetic components within both the offspecular and transmitted components. Figure 13 shows the spin dependent angle vs. wavelength maps taken at low incident angle for a sample in a field of 4.5kOe. A difference map reveals the magnetic nature of both the reflected and transmitted beams. Further more detailed experiments are now under way which aim to analyse both the polarised off-specular reflectivity and the small angle scattering from the nanoparticle assembly with the aim of obtaining as much information as possible.

Magnetisation of Iron Nanoparticles.

As with the behaviour of patterned magnetic multilayers an understanding of the interactions of assemblies of magnetic nanoparticles is important when considering new methods of increasing storage density. Boatner et al have prepared samples of single crystal iron nanoparticles embedded in a layer near the surface of an yttrium-stabilized zirconia host [36]. The particles have been shown to be well separated within the zirconia matrix and so exchange interactions are minimised. The behaviour of the bulk magnetisation of the nanoparticle layer upon the application of an external field may be modelled using only the magneto-static dipole interaction [37]. Initial experiments indicated that a layer with a substantial magnetisation exists be-

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4. Future Instrumentation at ISIS The second target station at ISIS [38] will be constructed over the next 3 years with first beam to target expected during 2007. The first wave of instrumentation includes recommendation to build three new reflectometers, polRef [39], OffSpec [40] and INTER [41]. These three instruments will be optimised to provide an estimated twenty times increase in performance when compared to the current instruments CRISP and SURF. Such a leap in performance will be particularly beneficial for PNR measurements where the limitation of small samples sizes coupled with the intrinsic flux limited nature of the source may inhibit certain parametric studies . Currently, we are further optimising the beamline design with particular attention to increased brightness and the reduction of background levels. In particular, the background generated by fast neutrons and gamma rays that currently inhibit the detailed study of off-specular reflection.

Further development of detector technology will also reduce measurement times, reduce backgrounds and increase the resolution of off-specular reflection measurements by making use developing microstrip and wavelength shifting fibre technologies.

Two of the proposed reflectometers will be able to perform PNR measurements, polRef and its associated sample environment will be fully optimised for this purpose and will enable detailed control of the neutron polarisation. OffSpec will be optimised for the study of off-specular reflectivity with a pair of high resolution 2D detectors and the implementation of the recently developed Spin Echo Resolved Grazing Incidence Scattering (SERGIS) technique, [42, 43, 44] which will enable the study of inplane structure on the nano-scale and the investigation of surface crystalline diffraction. The study of nano-scale inplane structure will be of particular value as the size of correlation that may currently be investigated is limited to above a few microns in many cases. It is envisaged that such an instrument will facilitate unique experiments particularly in the burgeoning field of soft condensed matter.

5. Conclusions In this review, we aimed to have illustrated the state of the art capabilities of polarised neutron reflectometry in the study of magnetic nano-structures as evidenced by recent work on the polarised neutron reflectometer, CRISP at the Rutherford Appleton Laboratory. It is clear that polarised neutron reflectometry is well placed to exploit the future issues raised by solid state physics. The future technological challenge is to address the complicated systems in nanotechnology (spin-electronics, patterned systems, tunnel junctions, nano-wires etc.) which are currently being fabricated. With the worldwide experience in polarised neutron reflectometry and the next generation of instrumentation the future is certainly exciting.

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6. Acknowledgements It is a pleasure to thank our colleagues for many enjoyable solid state physics hours on the beamline and for their permission to present recent results. In this latter respect we particularly thank Prof. B.J.Hickey, Dr. C.H. Marrows, Dr. P.Steadman, Dr. M.Ali, Dr. A.T.Hindmarch, Dr. A.Potenza (Univ. of Leeds), Prof S.L.Lee and Dr. A.Drew (St. Andrews Univ.) and Dr. J.P.Goff, Dr. P.Deen (Univ. of Liverpool), Dr T.R.Charlton (Argonne National Lab./RAL), Dr. M.Takeda (Tohoku Univ.), Dr. N.D.Telling (Daresbury Lab.) and co-workers. We (and our co-workers) are grateful to the EPSRC for the provision of beamtime.

References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

G.P. Felcher et al. Rev. Sci. Inst. 58, 609 (1987) S.J. Blundell and J.A.C. Bland Phys. Rev. B. 46, 3391 (1992) C.F. Majkrzak, Physica B. 173, 75 (1991) G.P. Felcher J. Appl. Phys. 87, 5431 (2000) H. Zabel and K. Theis-Bröhl J. Phys. C. 15, 505 (2003) R. Felici et al. Appl. Phys. A 45, 169 (1988) V. Nunez et al. Physica B 241-243, 148 (1998) M.N. Baibich et al. Phys. Rev. Lett. 61, 2472 (1988) P. Bruno, Phys. Rev. B 52, 411 (1995) P. Zahn et al, Phys. Rev. Lett. 80, 4309 (1998) C.H. Marrows et al., IEEE Trans. Magn. 33, 3673 (1997) Analysis code can be obtained from www.isis.rl.ac.uk /LargeScale/ C.H. Marrows et al. Phys. Rev. 62, 11340 (2001) J.C. Slonczewski, Phys. Rev. Lett. 67, 3172 (1991) W. H. Meiklejohn and C. P. Bean, Phys. Rev. 102, 1413 (1956)

[16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32]

B. Dieny et al.J. Appl. Phys. 69, 4774 (1991) L. Lazar et al. J. Magn. Magn. Mater. 223, 299 (2001) P. Malozemoff, Phys. Rev. B 35, 3679 (1987) D. Mauri et al. J. Appl. Phys. 62, 3047 (1987) P. Steadman et al. Phys. Rev. Lett. 89, 077201 (2002) J.P. Goff et al. J.M.M.M. 240 592 (2002) P.P. Deen et al. submitted to Phys. Rev. Lett.

M.P. Nutley et al. Phys. Rev. B. 49 15789 (1994) S-W. Han et al. Phys. Rev. B. 59 14692 (1999) S.L. Lee et al ISIS Annual Report 2002 S.G.E. te Velthuis et al, J. Appl. Phys., 87, 5046, (2000) H. Fritzsche et al, Langmuir, 19, 7789, (2003) S.K. Sinha et al, Phys. Rev. B, 38, 2297, (1988) V. Holy et al, Phys. Rev. B, 49, 10688, (1994) R. Pynn, Phys Rev B, 46, 7953, (1992) M.K. Sanyal et al, Phys. Rev. Lett., 66, 628, (1991) J. Daillant and A. Gibaud, 1999, X-ray and neutron reflectivity: principles and applications (Springer-Verlag: New York) S. Langridge et al, Phys. Rev. Lett, 85, 4964, (2000) N. D. Telling et al, J. Appl. Phys., 93, 7420 , (2003) M.J. Bonder et al , J. Appl. Phys., 93, 7226 , (2003) S. Honda et al., Appl. Phys. Lett., 77, 711, (2000) T.C. Schulthess et al,. J. Appl. Phys., 89, 7594, (2001) www.isis.rl.ac.uk/targetstation2/ www.isis.rl.ac.uk/targetstation2/instruments/POLREFweb. pdf www.isis.rl.ac.uk/targetstation2/instruments/OFFSPECweb.pdf www.isis.rl.ac.uk/targetstation2/instruments/INTERweb.pdf M.Th. Rekveldt, Physica B, 234–236, 1135, (1997) J. Major et al., Physica B, 336, 8, (2003) R. Pynn, et al, Rev. Sci. Inst., 73, 2948, (2002)

[33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44]

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Paper received March 2004

THE INFRARED BEAMLINE SISSI AT ELETTRA S. Lupi1, A. Nucara1, L. Quaroni2, and P. Calvani1 1

COHERENTIA-INFM and Dipartimento di Fisica Università di Roma La Sapienza, P.le A. Moro 2 00185 Roma, Italy

The Synchrotron Infrared Beamline SISSI (Source for Imaging and Spectroscopic Studies in the Infrared) under construction at ELETTRA, has been developed through a collaboration be tween the COHERENTIA-INFM group of the University of Rome La Sapienza and the Sincrotrone Trieste S.C.p.A. SISSI will be devoted to a multidisciplinary use, ranging from Material Science, Chemistry, Biology, Archeometry to Industrial Applications. The beamline collects the radiation emitted from a bending magnet in a wide solid angle (65 mrad x 25 mrad) providing a high photon flux from the far infrared to the visible (1 meV-3 eV). The experimental station consists of a Bruker IFS-66v Michelson Interferometer associated with a Hyperion 2000 infrared microscope. The high brightness of the infrared synchrotron source coupled to the microscope will permit to probe absorbing materials with a spatial resolution close to the diffraction limit in the infrared.

Introduction Infrared spectroscopy is an extremely powerful technique since infrared radiation couples directly with certain vibrational modes of molecules. By measuring the frequency of these modes, “finger-print”of the molecules can be obtained leading to their identification in many materials. Moreover, infrared radiation probes the lowlying states of solids (phonons, quasi-electrons, polarons, etc.), the interaction between a surface and an adsorbate, and many other low-energy characteristics of basic importance for Condensed Matter Physics, Chemistry, Biophysics, Geology, Archaeometry and Industrial applications.

Infrared Spectroscopy has a long history. Infrared phononic spectra were collected already at the end of the nineteenth century by E. Nicol and published on the first page of the first issue of Physical Review.[1] However, the measurements of infrared spectra, through the 1970s were based on prism or grating monochromators, which present a low energy throughput in the infrared. A major breakthrough in infrared technology was made in the Sixties with the introduction of the Michelson Interferometer (FT-IR) coupled to a personal computer performing the Fourier transform. A Michelson interferometer presents several advantages in comparison with a grating monochromator or a prism. In particular the socalled Jacquinot (or throughput) advantage arises as the

2

Sincrotrone Trieste S.C.p.A., S.S. 14 Km 163.5, in Area Science Park, 34012 Basovizza Trieste, Italy

circular apertures used in FT-IR spectrometers have a larger area than the linear slits used in prism or grating monochromators, thus enabling higher throughput of radiation. Moreover in prism or grating spectrometers, the power spectrum I(ν) is measured directly by recording the light intensity at different frequencies ν, one ν after the other. In FT-IR, all frequencies coming from the source illuminate simultaneously the detector. This accounts for the so-called multiplex or Fellget advantage.

However the only available sources used in the infrared through the 1980s were Globar and Mercury lamps. A Globar source approximates a black body heated at about 1500-2000 K, and presents a power spectrum with a maximum around 2000 cm -1. The emitted intensity quickly decreases in the far-IR for frequency ν < 500cm-1.

The same intensity decrease is shown by the mercury source below 200 cm-1. Moreover, since the power spectrum is emitted under a solid angle 4π, the brightness of the source is low and only a small portion of the intensity can be focused on a sample. Therefore experiments, which require a high flux and/or brightness, such as for strongly, absorbing samples, for reflectance measurements at grazing angle, or with High Pressure Anvil Cell, may present a poor signal-to-noise ratio. In those cases where the experiment requires a “white spectrum”, the Infrared Synchrotron Radiation (IRSR) provides a high brightness source over a broad spectral range.[2] In spite of the high intensity, synchrotron infrared radiation does not degrade the sample because it does not break any chemical bond or changes noteworthy the equilibrium temperature. Indeed experiments show that focused IRSR increases the temperature of living cells of a maximum of 0.5 K.[3] The negative effects of the low brightness of a thermal source are more evident in infrared microscopy, a technique that dates back to the Seventies. So far a good signal-to-noise ratio can be obtained with thermal sources only for samples bigger than 50x50 µm2, namely much larger than the diffraction limit in the mid-infrared. Instead that limit can be obtained by using the high brightness of the infrared synchrotron source coupled to the IR microscope.

Extraction of IRSR is presently performed in most synchrotron rings.[4] Surface Science using IRSR has been developed at NSLS (Brookhaven, USA) and Daresbury

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(UK). High Pressure measurements have been performed at UVSOR (Japan) and NSLS. IRSR Spectromicroscopy applied to Biology, Medicine and Forensics has been improved at ALS (Berkeley, USA) and LURE (France) as well as at BESSY-2 (Germany). Finally, Condensed Matter Far-IR spectroscopy has been developed at SRC (Wisconsin, USA), LURE, ANKA (Germany), Spring-8 (Japan), DAΦNE (Frascati, Italy). This list of IRSR beamlines is far from being complete, since new beamlines are planned or under construction on SLS (Switzerland), ESRF (France), and at the Canadian Light Source. In this paper we present the project of the infrared beamline SISSI under construction at ELETTRA (Trieste, Italy) and we discuss the scientific role that this IR facility may play for both the Italian and the European scientific community.

1. Characteristics of IRSR Most of the IRSR beamlines already operating have been built on second or third generation synchrotrons, where infrared and visible radiation is extracted from a bending magnet in a wide solid angle. Synchrotron radiation emitted by a bending magnet covers a broad spectral range from X-rays down to infrared and submillimeter frequencies. In this case the Schwinger equation holds and the emitted spectral intensity versus the energy E consists of a featureless continuum decreasing roughly as E5/3. However, the natural emission angle of the synchrotron radiation, which is of the order of a few mrads in the X-rays, opens up as a function of the wavelength.[5] It increases to several tens of mrads in the infrared, depending on the radius of the ring following the approximate law:

tual Brightness Ratio) has been addressed to be the most important figure of merit of an IRSR beamline. An ABR value of the order of 100 has to be achieved in order to obtain the maximum spatial resolution with a confocal infrared microscope corresponding to the diffraction limit of about 0.78λ.

Another worthwhile figure of merit for IRSR beamlines is the polarization degree (PD) of the radiation. It depends on the emission properties of IRSR as well as on the optical and geometrical characteristics of the beamline. As a general rule, the radiation collected from a bending magnet under a small vertical angle is linearly polarized on the plane of the particle orbit, while the offaxis radiation is elliptically polarized, with a PD value which strongly depends on both the photon energy and the vertical acceptance angle. In the limit of large vertical angle (> 20 mrad) the off-axis radiation is purely circularly polarized. Circular polarization is of fundamental importance in several fields of research spanning from vibrational spectroscopy in chiral and biological systems to far-IR spectroscopy in magnetic and superconductors materials.[7,8] Finally, an important feature of IRSR is its pulsed structure. The electronic bunches at ELETTRA may be injected with a HWHM of about 50 ps and at a rate of tens of ns. This bunch structure corresponds to photon pulses with the same time structure, which can be used as trigger for pump-probe experiments as well as to study nanosecond time-scale infrared response of various materials.[9]

λ θ nat ( rad ) = 1.66( )1 / 3 ρ

where λ is the wavelength and ρ is the radius of curvature of the bending magnet (in the same units as λ). ΘNat is the angle required to transmit 90% of the emitted light at the given wavelength.[6] The ELETTRA ring has a dipole radius of 5.5 m, corresponding to a value for Θnat of 13 mrads in the mid-infrared at 500 meV, and to 35 mrads at 25 meV in the far-infrared. Extracting radiation under such angles has been a limiting factor in the development of far-IR synchrotron sources in third generation machines, since large apertures in the vertical direction of the bending chambers may degrade both the stability and the lifetime of the electron beam.

The main characteristic of IRSR, in particular for microspectroscopy applications, is the brightness. Brightness is defined as the photon flux per unit solid angle and per unit source area. The brightness gain of IRSR with respect to a conventional infrared source (ABR, Ac-

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Fig. 1. The infrared photon flux F collected from bending magnet 9.1 of ELETTRA for an energy of the electron beam of 2 GeV. The flux from the ALS source and from a Black-Body lamp are shown for comparison.

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2. The IR beamline SISSI at ELETTRA The beamline SISSI collects the infrared radiation emitted from the 9.1 bending magnet of ELETTRA.[10] The extraction geometry of the beamline is shown in Fig. 1.

The vacuum bending chamber has been modified in order to obtain a large emission angle of 65*25 mrads2 which fit the natural divergence of the synchrotron radiation in the infrared. This vertical angle is such that the 70% of the total flux at 25 meV will be collected without any reduction in the stability and lifetime of the electronic beam.

The IRSR flux from the 9.1 bending as a function of frequency is shown in Fig. 2 for an electron beam energy of 2 GeV. In the same figure the flux radiated from the ALS beamline and from a Black-Body (BB) source are shown for comparison. Although the power intensity of IRSR drops gradually for decreasing energies according to E5/3, the intensity of a BB source decays with E more rapidly, following an exponential law. The IRSR intensity becomes higher than the BB one in the far-IR, for energies below 20 meV. The flux gain of IRSR in the far-IR may be used in several fields of research: for instance to probe the conformational modes of proteins, RNA and DNA molecules dissolved in strongly absorbing aqueous solutions.

However, as discussed in the last section, the main figure of merit for an infrared beamline is the brightness. It depends on the spatial distribution of IRSR and also on the transfer optics of the beamline. The optical layout of SISSI is reported in Fig. 3. Assuming the waist of the particle beam in the bending magnet as the origin of the longitudinal coordinate, the first vacuum chamber is placed at 350 cm: this short distance, chosen in order to minimize the mirror dimensions, allows one to reduce

Fig. 2. The geometry adopted for the extraction of the infrared radiation.

The dashed area represents the horizontal collection angle subtended by the extraction mirror placed at 350 cm from the center of the particle trajectory. The dotted-dashed line corresponds to the straight section upstream to the bending magnet. The magnetic field profile at the entrance of the bending magnet is shown in the inset. Therein the trajectory delimited by the dotted line is that selected by the horizontal collecting angle.

the length of the beamline front-end to about 150 cm.

The first mirror (M1) placed in the chamber collects the infrared radiation emitted from the bending magnet. M1 presents a slit of 5 mm on the central part of the mirror body in order to reduce the thermal load. This slit transmits the intense X-ray bending emission thus preserving

Fig.3. Layout of the SISSI infrared beamline at ELETTRA.

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the optical performance of the beamline. IRSR is deflected by M1 of 90 degrees towards an ellipsoidal mirror (M2) placed at 100 cm from the previous one and mounted in the same vacuum chamber. M2 focuses the radiation at the focal point F1 placed at 1150 cm, beyond the shielding wall of the synchrotron hall. The radiation is then collected by the mirrors M3 and M4, which are both contained in a second vacuum chamber placed at 1450 cm from the source, and finally focused at the entrance F2 of the Michelson interferometer at 1550 cm from the origin. At F2, a CVD diamond window separates the ultra high vacuum part of the beamline (which is kept at the same pressure as the synchrotron) from the low-vacuum side of the interferometer. Both the characteristics of the mirrors and the optical transport properties of the beamline have been studied by ray-tracing simulation.

The main mirror parameters are reported in Table I.

The spatial distribution of IR photons obtained at F2 by ray tracing simulation is reported in Fig. 4a. Neither the vertical, nor the horizontal angular distribution at F2, shown in Fig.4b and Fig.4c, exceeds 0.07 rad, allowing the use of an interferometer with a large f-number. Owing to the large horizontal extension of the IRSR source, the image is affected by a quite small coma aberration in the horizontal dimension. On the contrary, the ray distribution along the vertical coordinate is quite symmetric.

The reduction of the geometrical aberrations is a crucial point for infrared microscopy, as the symmetry and the homogeneity of the photon distribution at the sample site improve the spatial resolution.

The values of brightness gain ABR can be calculated as a function of the size D of an aperture located in the sample compartment of the interferometer. This approach simulates a real experiment and takes into account the ray distribution of IRSR at the sample site, which depends on aberrations, surface distortions, and misalignments of the beamline optical system.[10] In particular

Figure

Dimension

Surface parameters (cm)

HxV (cm2) Mirror 1

plane

30x15

Mirror 2

ellipsoidal

35x18

Semi major axis: 625 Semi minor axis: 424

Mirror 3

plane

15x8

Mirror 4

ellipsoidal

16x10

Semi major axis: 250 Semi minor axis: 141

Table 1

TFig. 4. Spatial (a) and horizontal (b) and vertical (c) angular ray distribution of the IR photons at the entrance of the interferometer.

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Fig. 5. Actual brilliance ratio ABR of the SISSI beamline, calculated at several energies for a collecting angle of 65x25 mrads.

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we have considered the measured slope error for each surface mirror. Moreover the value of ABR gives an insight of the sample size D for which, at a given wavelength, the use of IRSR is mandatory. In Fig. 5 the values of ABR for SISSI are reported at different energies as a function of D. As shown in the figure, the advantage of the IRSR brightness becomes effective for an aperture D ≤ 1 mm where gains of the order of 102-103 can be obtained.

For this reason we expect that the beamline will be particularly suitable for microscopy with spatial resolution at the diffraction limit both in the mid and in the far-IR. Another important figure of merit is the polarization degree PD of the infrared light. Since the polarization degree depends on the vertical emission angle, a rectangular slit will be placed 50 cm after the ellipsoidal mirror M2 in the first chamber. The slit, with a fixed aperture of 24 × 0.3 cm2 (H×V), can be vertically displaced from the optical axis of the beamline. The slit allows one to select the off-axis radiation at a given vertical angle. In Fig. 6, both the linear and circular PD at F2 are reported as a function of energy. As expected, the linearly polarized character of IRSR is more evident in the case of a small aperture angle, since the beamline front-end mostly collects on-axis radiation. Since the Michelson interferometer substantially preserves the polarization properties of the radiation, experiments using both linear and circular polarization can be performed at the sample site. The

Fig. 6. Linear (a) and circular (b) polarization degree PD estimated as a function of the vertical collecting angle f and for several photon energies.

SISSI beamline, up to the entrance of the interferometer, has been entirely funded by Sincrotrone Trieste SCpA. 3. Experimental station The experimental station of the SISSI beamline has been fully financed by a joint contribution of the COHERENTIA-INFM center and of the INFM-PURS project. The apparatus consists of a Bruker IFS/66v Michelson interferometer coupled to a Hyperion 2000 infrared microscope. The spectral range from the very far-IR to the visible 5 to 25000 cm-1 (1 meV-3 eV) is covered with a spectral resolution of 0.25 cm-1 (30 µeV). Time-resolved spectra down to nanosecond time scale can be obtained in the mid-IR using the step-scan capability of the interferometer coupled to fast electronic and detectors. The Hyperion 2000 infrared microscope associated to IRSR light, which provides a spatial resolution of a few microns, has been also equipped for fluorescence measurements in the visible range. The optical setup permits a number of different experiments spanning from transmission to reflectance measurements at normal and variable incidence angle.

4. Scientific activities The unique characteristics of IRSR allows one to perform a number of experiments, that are prevented when using a conventional thermal source. Moreover, IRSR also provides a better signal-to-noise ratio and a reduction of the acquisition time in more standard experiments. As discussed in the introduction, IRSR spectroscopy permits extensive applications in several fields of research. Here, we review some recent experimental results obtained with IRSR and we describe the scientific opportunities opened by the SISSI project to the Italian and European community.

4A. Solid State Physics a) High Tc Superconductors (HCTS), Colossal Magnetoresistence Manganites (CMR) and other exotic electronic materials are presently extensively studied in order to investigate the role of charge localization and charge-ordering in their anomalous properties. A major contribution to this field is given by infrared spectroscopy, which monitors the low-energy excitations of these systems, the presence of gaps in the optical conductivity σ(ω) and the formation, below a certain temperature, of charge collective modes. The σ(ω) is obtained from Kramers-Kronig transformation of the measured reflectance. An example of this “low-energy” behavior is shown by recent data in the High Tc Superconductor Bi2Sr2CuO6 (BSCO).[11] These data lead to a new picture of the transport properties of cuprates. In the past, the optical conductivity of HCTS has been described by a single component and

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analyzed in terms of an anomalous Drude model in which both the scattering rate Γ and the mass m of charge carriers depend on frequency. Instead in BSCO, measured down to 10 cm-1and reported in Fig. 7, two well separated contributions are well evident in the optical conductivity. The first term is a narrow Drude component with a width Γ=35 cm-1 at 30 K, in very good agreement with transport data. The small value of Γ is consistent with a metal in an extremely clean limit, where the carriers move in a well ordered, nearly defect free Cu-O plane. The second component is a strong band centered in the far-IR at about 100 cm-1, likely due to a charge collective mode. Below the critical temperature Tc both the Drude term and the

tive mode. In the spectroscopic studies of HCTS and related compounds, the use of IRSR allows a complete coverage of the whole reflectivity spectrum from 10 to 10000 cm-1, in a single experiment performed on a small sample. Moreover circular polarization of IRSR in the far infrared, which cannot be obtained with conventional thermal sources, may open new opportunities in the spectroscopic studies of magnetic, superconducting and chiral materials. b) Among the various phenomena exhibited by matter under extreme pressure conditions, one of the most intriguing is the occurrence of the Insulator-to-Metal transition (IMT). The development and the availability of simple high-pressure equipment have stimulated

Fig. 7. The optical conductivity σ(ω) of a thick film of Bi2Sr2CuO6, as extracted from the reflectivity measurement R(ω) by Kramers-Kronig transformation (from Ref. 11). The full triangles represent the measured DC conductivity. The open circles denote the best fit to a normal Drude term here proposed only for the 30 K curve.

collective mode lose spectral weight (SW) in favor of the superconducting δ -peak mode centered at zero frequency. The lost of SW indicates that the superconducting transition affects both terms and that the charge transport is determined by a superposition of a single particle Drude contribution and of a collec-

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in the last two decades a large amount of experimental work in this field. In particular the metallization phenomena in halogen phases (liquid I2, Cl2 and Br2) is the most interesting one, since the pressure needed to induce the transition matches quite well the maximum pressure obtainable by an Optical Anvil Cell

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(about 200 GPa).[12] In this case the effective dimension of the samples (determined by the diamond surfaces), is of the order of 100 microns or lower. Therefore infrared spectroscopy utilizing IRSR has emerged as an important new tool in the panorama of High Pressure Physics. In fact the high brilliance of IRSR results in major improvements in the probing of these small samples, and provides the maximum accessible signal-to-noise ratio. One may cite the determination of the phase diagram of solid hydrogen up to 200 GPa at Brookhaven by Hemley and collaborators. The IRSR results exclude any metallization of solid H2 up to those pressures.[13] 4B. Earth Sciences Environmental and earth sciences are research fields where IRSR microspectroscopy can find a great number of applications. IRSR microspectroscopy can be consid-

Fig. 8. Change of the Cu(001) single-crystal reflectivity induced by the adsorption of 0.5 monolayers of CO. The spectrum shown in the Figure has been measured at grazing incidente angle at the U4IR beamline of Brookhaven (from Ref. 16).

ered as the only non-destructive tool for investigation of interaction at the bacterial-mineral interface, where the small spot of infrared radiation is suitable to collect spectra on sample areas where microorganisms are present.

Another example is the study of meteoritic fragments collected by the Italian expedition to the Antarctic, re-

cently performed under a collaboration between the University of Rome La Sapienza and the Daresbury (GB) IRSR beamline. This study has provided information about the chemical composition of the meteorite and the conditions under which it was formed.[14] 4C. Surface Science The combination of chemical sensitivity with the IRSR polarization properties can be successfully applied in studies of anti-corrosion and on catalytic processes occurring at gas/solid, gas/liquid, and liquid/solid interfaces. These studies are of interest for basic research as well as for technology applications. The orientation of molecules at an interface is of key importance to any microscopic description of surface chemical reactions. The intermolecular forces among the adsorbed molecules and among the molecules and the surface determine that orientation. Thus, IRSR can be a very useful technique to study the ordering and the orientation of organic and polymer molecular layers. These layers are important for the understanding of the mechanism of catalytic reactions, where the adsorbed molecules increase the chemical and the physical stability of the materials and are often used as protective layers. Since the adsorbed molecules are orthogonal to the surface, in order to probe their absorption the electric field of the radiation should be aligned along their molecular axis. This implies that the radiation must propagate nearly parallel to the surface, i.e. at grazing angle of incidence. Moreover, since the IR absorbance of the molecular modes is small, the change in the reflectance induced by a single monolayer of adsorbate is of the order of 0.1 %, and high brightness is required to obtain an adequate signal-to-noise ratio. In Fig. 8 we show the reflectance changes induced by a monolayer of Co on Cu(110) between 50 and 500 cm-1 measured at the Brookhaven IRSR beamline.[15,16] The peak at about 300 cm-1 is due to the hindered rotational mode of CO, while the minimum at about 350 cm-1 corresponds to the carbon-metal vibrational mode. Both the reference spectrum for the clean Cu and the adsorbate spectrum have been taken in 80 s with reproducibility of the order of 0.01%.

4D. Biology and Medical Applications The non-destructive character of IRSR makes it attractive also for biological and medical applications, since it combines a sufficiently small spot size with the possibility of extracting information on chemical composition.

One of its most spectacular application, the spectrum of one living cell, has already been performed with IRSR microscopy.[17] In Fig. 9a we report the photograph in the visible of an elongated mouse hybridoma cell undergoing mitosis. The corresponding vibrational absorption spectrum is reported in Fig. 9b. Here we observe the

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amide I (1650 cm-1) and amide II (1540 cm-1) absorption bands which indicate the presence of proteins. The amide II distribution map is shown in Fig. 9c and presents a symmetric distribution around the two nuclei of the cell. The absorption band at 2925 cm-1 is characteristic of the C-H methyl group corresponding to the lipid membrane. The distribution map of lipids (Fig. 9d) shows a peak in the absorption at the center of the cell, probably indicating the formation of a new cell wall due to mitosis.

Moreover the opportunity to perform time-resolved Fourier transform infrared experiments (TRFT) in combination with a fast-mixing continous-flow microfluidic device for analysis of reaction intermediates in solution, will provide invaluable insight into protein structure and dynamics. The TRFT method is complementary to real-time NMR and circular dichroism (CD). In contrast to NMR, which provides time-averaged information, infrared spectra are not affected by averaging of flexible states. By combining information obtained from infrared studies with those from the CD method, structural elements in folding intermediates can be fully described.

The possibility of detecting native as well as not native structures at the same time is especially valuable in gaining insight into the complexity of the refolding process

of a protein. Moreover, non native b-sheets, which present a transient character down to a nanosecond time scale, may be detected with the combination of the timeresolved capability of the experimental station of SISSI and the pulsed-time structure of IRSR. Recently the potential of vibrational microspectroscopy with IRSR to supplement, if not to replace, the conventional methods of histological and cytological characterization in human diseases, has been reviewed.[18] In fact diseases usually begin with a single cell, in which both the chemical composition and its interaction with the surrounding tissue changes. Therefore IRSR imaging techniques coupled with fluorescence measurements (which can be performed with the same IR microscope) may simultaneously provide both morphological and chemical information about a single diseased cell and separate its behavior from that of healthy cells. In this area a lot of work has been done on the screening of cervical cells, oral cells and bone for evidence of malignancy and premalignancy.[19] 4.E Archaeometry The use of IRSR radiation offers a powerful non-destructive method for the study and the conservation of cultural heritage. In particular spectromicroscopy permits the

Fig. 9. Photograph of a living cell (a). Its transmission spectrum in the mid-IR is shown in (b). The spatial distribution in the cell of the amide II protein band at 1540 cm-1 (c) demonstrates the increased concentration around the two nuclei. The spatial distribution in the cell of the absorption band of lipids at 2925 cm-1(c), shows the increased concentration between the two nuclei, suggesting the formation of a cellular wall (from Ref.17).

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analysis of tiny samples in different forms such as pellets, powders and solid particles, the determination of particle and fiber composition in archaeological findings and the analysis of complex materials such as paints, pigments, ceramics and ancient papers.[20] For instance the analysis of the interaction of inks and papers to which they are applied is of a great interest in archaeometry. In particular a spatial resolution ≤20 mm is much smaller than any line made on a paper by normal pens and much smaller than the worst case of a single dot of ink.[21] In Fig. 10 we show the infrared absorption spectrum of ink on a paper fiber using both synchrotron and Globar sources. The superior sensitivity and resolution of the synchrotron based approach is well evident in the analysis of the ink spot with a spatial resolution of about 10 µm. The spectral range between 1000 to 4000 cm-1 contains multiple vibrational bands of C=C, C=N, C-O, C=O, C-N, C-S, S-O bonds and their overtones and combination bands.

Fig. 10. Mid-IR absorption spectra of ink on a paper fiber using IRSR and a Globar source. The IRSR spectrum, measured at the ALS infrared beamline (from Ref. 21), due to the much better spatial resolution, provides information about the chemical composition of ink.

5. Conclusion The successful use of Infrared Synchrotron Radiation as a bright, pulsed, broadband source for spectroscopy and imaging applications is evident from the number of facilities already operating or under commissioning in the world. On this ground the SISSI Infrared beamline, which will be assembled during the next Summer at ELETTRA, opens a new scientific perspectives for the Italian and European scientific community.

Acknowledgment The authors wish to thank the technical staff of ELETTRA for their help in the optical and mechanical project of the beamline and in the realization of the support infrastructure.

References [1] E. F. Nicol, Phys. Rev. 1, 1 (1893) [2] G.P. Williams, Nucl. Instrum. Methods A, 291, 8 (1990) [3] H.-Y.N. Holman, M.C. Martin, E.A. Blakely, K. Bjornstad, and W.R. McKinney, Biopolymers (Biospectroscopy), 57, 329 (2000) [4] See, for example, Infrared Synchrotron Radiation, edited by P. Calvani and P. Roy (Compositori, Bologna 1998), and references therein.

[5] W.D. Duncan and G.P. Williams, Appl. Optics 22, 2914 (1983) [6] U. Schade, A. Roseler, E. H. Korte, M. Scheer, and W. B. Peatman, Nucl. Instrum. Methods 72, 1620 (2000) [7] S. Kimura, UVSOR Activity Report 1997, BL6A1, p. 170 [8] S. Kimura, D. X. Li, Y. Haga, and T. Suzuki, J. Magn. Mater. 177, 3121 (1998) [9] G. L. Carr, R. P. S. M. Lobo, J. LaVeigne, D. H. Rejtze, and D. B. Tanner, Phys. Rev. Lett. 85, 3001 (2000) [10] A. Nucara, S. Lupi, and P. Calvani, Rev. Sci. Instrum. 74, 3934 (2003) [11] S. Lupi, P. Calvani, M. Capizzi, and P. Roy, Phys. Rev. B 62, 12418 (2000) [12] U.Buontempo, E. Degiorgi, P. Postorino, M. Nardone, Phys. Rev. B 52, 874 (1995) [13] H. K. Mao, and R. J. Hemley, Rev. Mod. Phys. 66, 671 (1994); A. F. Goncharov, R. J. Hemley, H.K. Mao, and J. Shu, Phys. Rev. Lett. 80, 101 (1998) [14] A. Maras, M. Macri, P. Ballirano, P. Calvani, S. Lupi, P. Maselli, B. Ruzicka, M. J. Tobin, and M. A. Chester, Proc. of the 64h Annual Meteoritical Society, p.5203 (2001) [15] F. M. Hoffmann, B. N. J. Persson, W. Walter, D. A. King, C. J. Hirschmugl, and G. P. Williams, Phys. Rev. Lett. 72, 1256 (1994) [16] P. Dumas, M. K. Weldon, Y.J. Chabal, amd G. P. Williams, Surf. Rev. Lett. 6, 225 (1999) [17] L. Carr, P. Dumas, C. J. Hirschmugl, and G. P. Williams, Nuovo Cimento D 20, 375 (1998) [18] D. L. Wetzel, and S. M. LeVine, Science 285, 1224 (1999) [19] R. K. Dukar, in Handbook of Vibrational Spectroscopy, Vol. 5, eds. J. M. Chalmers, and P. R. Griffiths, John Wiley & Sons, Ltd., U.K., 3335 (2002) [20] M. R. Derrick, D. Stulik, and J. M. Landry, Infrared Spectroscopy in Conservation Science, ed. by The Getty Conservation Institute, Los Angeles (1995) [21] 0T. J. Wilkinson, D. L. Perry, M. C. Martin, W. R. McKinney, and A. A. Cantu, Appl. Spectrosc. 56, 800 (2002)

Source The optical parameters of the SISSI mirrors, as calculated by SHADOW ray-tracing routine.

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Paper received May 2004

COMPLEX DYNAMICS IN POLYMER ELECTROLYTES A. Triolo1, O. Russina2, M. Lanza1 and H. Grimm3 1

Istituto per i Processi Chimico-Fisici, Consiglio Nazionale delle Ricerche, via La Farina 237, 98123 Messina, Italy

We report high resolution Fixed Energy scans from a random block copolymer both in its pure and salt-doped state.

Inelastic as well as Elastic Fixed Energy scans from the BSS spectrometer at Juelich are described in terms of a wealth of relaxation features, indicating the dynamic complexity of polymer electrolytes.

The original approach used to quantitatively model inelastic fixed energy scans and the comparison with broadband dielectric spectroscopy allow detecting the heterogeneous features of the α-process in polymer electrolytes.

Introduction Polymer electrolytes (PEs) represent a new class of composites whose performances are presently attracting a great deal of interest: their conductivity performances make them ideal for applications such as secondary batteries, electrochromic windows and other electrochemical devices. They are obtained by mixing of poly-ether macromolecules (e.g. polyethylene oxide, PEO) and salts, such as Li triflate [1].

The ether units of the macromolecules have been shown to wrap around the salt cation, thus performing an efficient solvating role, leading to salt solutions in a highly mechanically stable polymer matrix [1]. Such mechanical performances and the possibility of obtaining very thin PEs films which can efficiently chemically interact with anode and cathode electrodes make PEs extremely appealing for a variety of applications.

The conduction process is believed to be mainly associated to the cation diffusion under the influence of an external electric field [1]: in many PEs the salt is suitably chosen to have a bulky, essentially immobile anion, whose contribution to conductivity becomes negligible. In these conditions, the cation diffusion is strongly related to those polymer segmental motions which, unwrapping the cation, can set it free to move. Such relaxation processes occur on a nanosecond time scale in the liquid state, while they are drastically frozen in the crystalline state.

Accordingly, in order to get an efficient cation diffusion a negligible crystalline fraction should be present in the PEs. On the other hand, when dealing with PEO a large portion of the molecules are organised in a crystalline way at the normal operational conditions (i.e. below 60°C). This implies that the salt cation remains immobile

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Hahn-Meitner Institut, Glienicker str. 100, 14109, Berlin Germany 3 Institut fuer Festkoerperforschung, Forschungszentrum Juelich GmbH, D-52425 Juelich, Germany

as it is efficiently wrapped by frozen crystalline chains.

There are different approaches leading to a decrease of the crystalline fraction in common poly-ethers. Addition of small ether oligomers can lead to an increasingly local disorder which prevents efficient molecular packing and, as a consequence, crystallization. Though this approach is efficient in preventing crystallization, still leakage of the low molecular weight oligomers progressively occurs, leading to a worsening of the device performances. Alternatively addition of inert fillers, such as silica or alumina, has been found to significantly decrease the crystalline fraction and to efficiently improve the mechanical properties of the PEs. A further approach consists in using specifically engineered polyether macromolecules, whose crystalline fraction is very low. For example, while PEO is a semicrystalline, polypropylene oxide (PPO) is fully amorphous. Accordingly a block copolymer, where different fractions of PEO and PPO are randomly connected, can be synthesised so to be characterised by negligible crystalline fraction. In this communication we will report on our recent efforts in the characterization of the relaxation processes in a random PEO-PPO block copolymer (pure and doped with LiN(SO2CF3)2) by means of complementary techniques such as Quasi Elastic Neutron Scattering (QENS) and dielectric spectroscopy.

In general the QENS technique provides information on single particle (mainly hydrogen atoms) dynamics on a temporal scale ranging from 10-13 to 10-8 s on a microscopic length scale (of the order of a few Å) [2]. Such a piece of information turns to be of fundamental importance in order to address details on fast dynamics in polymers and to derive information on the geometrical nature of the relaxation processes. As opposite to dielectric and other spectroscopies which may possibly cover a wider dynamic range, QENS is unique in providing information also on the spatial scale over which the process occurs.

Experimental A cross-linked poly(ethylene oxide-propylene oxide) random copolymer has been prepared as previously reported [3]. Both the neat sample and the one doped ([O]:[Li]=20:1) with lithium bis(trifluromethanesulfonyl)

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imide, LiN(SO2CF3)2, have been studied combining a variety of complementary techniques. The average molecular weight of the macromonomer is ca. 8000, and the ratio of PEO and PPO units is about 4:1. DSC measurements indicate that both samples contain only a negligible crystalline fraction and allow determining the glass transitions for the two samples: T g,pure =210 K and Tg,doped=230 K for the pure and salt-doped copolymer, respectively. Both Elastic and Inelastic Fixed Energy scans (EFES and IFES, respectively) at high energy resolution (1 µeV) were collected at the Backscattering Spectrometer (BSS) in FZ-Jülich, which is based on single crystal diffraction of cold neutrons with Bragg angles 2θ≅ 180° for monochromatization as well as energy analysis. A description of the BSS may be found elsewhere [4].

The BSS was used in the both in the elastic and inelastic fixed window modes (IFW). Concerning the IFW mode, the chosen monochromator (Si0.9Ge0.1-111) was kept at rest but its lattice spacing being slightly different from that of the analyzers (Si-111). This difference amounts to an energy transfer of ω = ωifw = -14.5 µeV. Both the pure and salt-doped polymer samples were contained in a slab aluminium cell with thickness d=0.2 mm. The scattered intensity S(Q,ωifw) was monitored as a function of sample temperature in the range 20 K < T < 450 K for the accessible range of momentum transfers Q (1.02<Q (Å-1)<1.89).

IFES on a polymeric sample have been reported earlier

by Grapengeter et al. [5], though no detailed analysis had been provided for those data. In their paper Grapengeter et al. [5] also provide a description of this

kind of experiments, highlighting the complementarity to the more common Elastic Fixed Energy scans [6].

Modelling of IFW-scans is based on a Cole-Davidson (CD) type susceptibility for the relaxation process [7]: χ’’(Q, ω)∝ωS(Q, ω)∝Im(1+iy)–b=f(y)

(1)

where y(T) = ωτ(T) with τ (T) describing the temperature dependence of the relaxation time and b representing the stretching of the relaxation process. For the IFW-scan y = ωifw τ(T) and introducing ym = ωifw τ(Tm) (Tm being the temperature at which the IFW-scan shows a maximum), one obtains for the measured intensity Iifw = S(Q, ωifw) = B + (Im – B) f(y)/f(ym) with f(y) = sin(b arctan(y))/(1 + y2)b/2

(2)

where B denotes the background being given by the intensity level at low temperatures and {Tm, Im} locate the maximum count rate. The function f(y) has a single maximum at ym which may be represented with sufficient accuracy in terms of the stretching exponent by ym = b-4/5 for 0.2 < b <2.0. For the relaxation time τ(T) one may assume an ansatz with 3 parameters, i.e. τ(Q,T) = τ o,α(Q) exp(A/(T-TVF))

(3)

with the attempt frequency 1/ τ o,α(Q), the apparent activation energy kBA and a Vogel-Fulcher temperature TVF. With the above approximation for ym , the stretching ex-

Fig. 1. Elastic Fixed Energy scans (EFES) collected at the BSS spectrometer on a pure sample of a crosslinked random block copolymer PEO-PPO at selected Q values. In the inset, the low temperature portion is highlighted, reporting the fit of the experimental data in terms of a model accounting for the methyl side group hopping process.

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ponent is related to those 3 parameters via the temperature Tm for the maximum intensity by ym = ωifw τ(Tm) = ωifw τ0 exp(A/(Tm-TVF)) ≅ b-4/5

(4)

It is straightforward to extend this description of the IFW-scan to more than one relaxation process, considering that each process can be described in terms of Equation 2. Dielectric spectroscopy data have also been collected on the pure rubber over a wide temperature range. AC isothermal dielectric measurements were carried out using a fully automated frequency response analyser (Schlumberger SI 1255) combined with a Chelsea Dielectric interface by Rheometric Scientific in the range 10-1-105 Hz and for 150< T(K) < 350. The pure polymer sample was disk like shaped (150 µm thick) and high purity gold was sputtered on its surfaces to form symmetrically blocking electrodes (diameter: 30 mm).

The frequency positions of the tangent delta peaks (tg δ= ε’’/ ε’) at each temperature have been obtained, in this preliminary communication, by fitting the experimental data with log-gaussian curves.

Results and Discussion In Figure 1 we report the elastic fixed energy scans (EFES) collected for the neat rubber sample at different Q values. These measurements consist in monitoring the amount of neutrons diffused by the sample without appreciable energy change. A non-linear decrease in this intensity is generally due to the occurrence of a relaxation process, leading to energy exchange between the

sample and the incoming neutron beam. A qualitative inspection of these data allows detecting three temperature regimes: a) a very low regime (I) (10< T(K)< 110), where only a linear decreasing of the EFES can be appreciated; b) an intermediate regime (II) (110< T (K) < 200) where a limited, non linear decreasing occurs and c) a late regime (III) (T> 200 K) where a large decrease of the EFES occurs. In regime I no relaxation processes occur and the linear decrease in the elastic intensity is due to the Lamb-Mossbauer effect, due to the vibrational motion of atoms around their equilibrium position.

Above 110 K (regime II), the clear decreasing of the EFES is related to relaxation processes occurring in the glassy material (Tg=212 K). As common in similar polymeric material, such processes can be related to highly localised motions either of sidegroups or of small chain portions. Eventually, above Tg (regime III), the distinct decrease of the EFES is related to the diffusive motion of chain portions, which relax without maintaining their centre of mass fixed.

In Figure 2 the inelastic fixed energy scans (IFES) for the same sample are reported for an energy exchange corresponding to λω=14. 5 µeV and different values of Q. The scenario emerging from the data in Figure 2 is qualitatively similar to the one derived from Figure 1. Following the interpretation of IFES provided in ref [5], it can be expected that the occurrence of a relaxation process corresponds, in IFES, to the presence of a peak. We stress that, to our knowledge, no quantitative modelling of IFES has ever been reported: by using the analytical approach described in the experimental section, we pro-

Fig. 2. Normalised Inelastic Fixed Energy scans (IFES) (ωifw=14.5 µeV) collected at the BSS spectrometer on a pure sample of a crosslinked random block copolymer PEO-PPO at selected Q values (from low to high: 0.86, 1.32, 1.54, 1.74, 1.88 Å-1). The curves have been vertically shifted for clarity. The continuous lines correspond to the fit in terms of the model outlined in the text, accounting for a low temperature process, related to the methyl group hopping, and a high temperature relaxation associated to the rubber-to-liquid transition. In the inset, the two fitting contributions are reported for the case of Q=1.88 Å-1.

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Fig. 3. Relaxation map for the neat crosslinked random block copolymer PEO-PPO sample. The two processes observed by QENS are reported for the case of Q=1.88 Å-1. The red line corresponds to the methyl group hopping and the blue line refers to the α-process. Also the contribution to the α-process arising as a consequence of salt addition is reported as a darkgreen line. Data from Dielectric spectroscopy are also reported. The three α, β and γ processes are indicated together with the temperature dependence of the conductivity. The continuous lines refer to Arrhenius (for β and γ relaxations) and Vogel-Fulcher (for the α relaxation and the conductivity) laws.

vide the first quantitative description of IFES in terms of a combination of Cole-Davidson relaxation processes. In particular the continuous lines reported in figure 2 correspond to a fit of the experimental data in terms of a combination of two contributions arising from a localised motion (low temperature contribution) and a diffusive process (high temperature one). In the present neat material, the PPO portions possess a methyl side group and the relaxation of this unit can be proposed as responsible for the low temperature feature in the IFES. In the literature, localised motions occurring in glassy polymers are often described in terms of the Rotational Rate Distribution Model [8], which accounts for the heterogeneity of the environment experienced by the relaxing units. We choose to model such an heterogeneity in terms of a stretching of the relaxation shape, by means of the Cole-Davidson law. The temperature dependence of the process has been described in terms of an Arrhenius law: τ Methyl = τ o,Methyl exp [Ea/kBT]

(5)

where Ea is the activation energy for the process. Due to the limited fraction of H atoms taking part to the process, the amplitude of the peak is small and the peak itself is covered by the much stronger feature related to the glass-liquid transition occurring at higher temperatures. Such a transition is generally found to be characterised by a strongly non-Arrhenius temperature depen-

dence and non-Debye shape. The high temperature portion of the IFES has then been modelled in terms of Eq. 2 and 3, describing the shape and temperature dependence of the relaxation, respectively. In the inset of Figure 2, a detailed description of the two fitting components is reported.

The low temperature process is characterised by a value for τ o,Methyl that shows no appreciable Q-dependence: such a feature is a consequence of the localization of the relaxation process, whose centre of mass does not diffuse. The activation energy for this process is 16.4 kJ/mol. This value is comparable with the corresponding parameters obtained for the methyl group relaxation in glassy polymers, showing a –CH3 unit directly connected to the polymer backbone [6].

The information extracted from the fitting of the IFES should be directly related to its EFES counterpart (Figure 1). Accordingly we tried to model the low temperature portion of the EFES using the fitting parameters extracted from the IFES data. As mentioned above the RRDM has been successfully employed to model methyl group hopping processes in glassy polymers. The local environment heterogeneity experienced by the hopping unit is modelled in terms of a distribution of relaxation rates.

This approach has been successfully applied to model EFES data from a number of glassy polymers possessing a methyl sidegroup [6,9] and has been shown to be equivalent to the approach involving a distribution of activation energies. In this case the EFES is modelled according to [10]: EFES(Q) = S(Q,ω~0) = Ao(Q) + 2 π-1 [1-Ao (Q)] arctg(Γr/Γ) where Ao(Q) is the elastic incoherent structure factor (EISF) accounting for the geometry of the hopping process: in the case of methyl group hopping around the C3v axis, we have: Ao(Q) = 1/3 [1+3jo(Q rHH)], where jo(x) is a spherical Bessel function of zero order and rHH is the distance between two H atoms on the methyl group (rHH =1.78 Å). Moreover Γ is related to the reciprocal of the characteristic time for the relaxation and Γr is the width of the instrumental resolution function. In particular, one has: Γ = Γo exp(- Ea/RT), Γo being the attempt to escape frequency and Ea the activation energy, which is assumed to be log-Gaussian distributed, according to: _ g(Ea,i) = [σ(2π)0.5]-1 exp[(Ea,i-Ea)2/2σ2],

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_ with Ea the average activation energy and σ the width of the log-Gaussian distribution.

Taking into proper account the fact that, below Tg, a fraction, χ, of the atoms are not relaxing and can be considered as frozen, one can model the experimental EFES _ data, using Ea, σ and χ as fitting parameters. The continuous lines reported in Figure 1 correspond to the fit of the experimental data in terms _ the model described above. In particular, we obtain Ea=17.5 kJ/mol and σ =5 kJ/mol. The value we derive for χ is not in agreement with the number of H atoms that belong to the methyl groups on the PPO units: this might imply that the probed motion is not fully attributable to the hopping CH 3 units, but might involve other highly localised processes.

In the higher temperature regime, the glass-liquid transition was satisfactorily modelled in terms of a VTF temperature dependence with the following parameters: A= 714 K and To=165 K. The relaxation shape is found to be strongly non-Debye like, with b=0.61. Moreover, as can be deduced from Figure 2 for this process, the characteristic time for the high temperature relaxation shows a distinct Q dependence: this is a consequence of the diffusive nature of the process. Accordingly we find that τo,α(Q) depends on Q following a power law: τo,α(Q)~Q-ν, with ν=1.8.

The relaxation map for the neat polymer sample is plotted in Figure 3. The two processes observed modelling

the IFES data are plotted and compared with data obtained using dielectric spectroscopy.

Dielectric spectroscopy (DS) provides a detailed picture of the variety of dynamic processes occurring in the material: for 150< T (K) < 330, up to four processes are highlighted by this technique (see Figure 3): in the low temperature regime, two processes can be detected which show an Arrhenius like temperature dependence; at higher temperature a strongly non-Arrhenius process occurs which can be interpreted as a local rubber-liquid transition and seems to behave as a trigger for the further conductivity process occurring at even higher temperatures. A detailed description of the dielectric relaxation map will be reported in a forthcoming communication. Here we aim to show the direct connection between the dynamic scenario probed by the QENS technique and the one obtained using dielectric spectroscopy. In particular, it is interesting to note the essentially quantitative agreement between the segmental dynamics probed by QENS and the one probed by DS: when fitting the two data sets with a VTF, one obtains: AQENS=714 K, log fo,QENS=11.81, To,QENS=165 K and ADielectric=712 K, To,Dielectric=165 K, log fo,Dielectric=11.13.

This result is relevant if one considers that the QENS data have been obtained fitting data collected at a very high frequency (f~109.5 Hz) as compared to frequency range accessible to the DS. QENS can also provide information on the spatial extent of the dynamics (through

Fig. 4. Comparison between the Inelastic Fixed Energy scans (IFES) (ωifw=14.5 µeV) collected at the BSS spectrometer on a pure sample of a crosslinked random block copolymer PEO-PPO and on the Li-triflate-doped sample at a selected Q value(Q=1.88 Å-1). The continuous lines correspond to fit of the experimental data in terms of the models outlined in the text. In particular, two contributions are considered for the pure polymer, while a third contribution, accounting for the salt-induced slow α-relaxation, has been considered for the salt-doped salmple. In the inset, a comparison between the Elastic Fixed Energy scans (EFES) for the same samples is reported.

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the ν parameter) that is not accessible to DS. Moreover QENS allows detecting the methyl group relaxation dynamics that is not probed by DS. In Figure 4 IFES and EFES (in the inset) data for both the neat and the salt-doped polymer are reported for a selected Q value. It can be noticed that for temperatures lower than about 200 K the two data sets do not show appreciable differences. This indicates that the dynamics in that frequency/temperature range is not affected by the salt addition: in view of our previous results, we can then state that the methyl group dynamics is not influenced by the transient crosslinks introduced by the salt. Above about 200 K the two samples start to differentiate themselves. In particular it emerges that the salt doped sample is characterised by a much slower dynamics: for this sample, the relaxation occurs at a higher temperature than required for the neat rubber. It is difficult to extract further information on the slow dynamics from the EFES data. On the other hand, further inspection of the IFES data can provide more useful information. A qualitative inspection of the IFES data shows that the salt-doped samples is characterised by a IFES spectrum that can be considered as built up by the combination of two contributions: a low temperature contribution that is centred at the same temperature where the neat sample α-process occurs and a higher temperature one. This behaviour can be interpreted considering that the salt addition leads to the formation of structural and dynamical microdomains, where the salt-induced transient crosslinks considerably slow down the segmental dynamics, that are embedded in a neat rubber matrix whose dynamics still resembles the one of the bulk pure rubber. Such a behaviour was already observed on the basis of DSC [11], PCS [12] and, recently, QENS [13] techniques for dilute salt-in-polymer solutions.

On the basis of this qualitative observation, we modelled the salt-doped IFES data using a model similar to the one used for the pure rubber, plus one additional CD (non-Arrhenius) contribution accounting for the high temperature salt-induced α -relaxation. In particular we assumed that the fitting parameters for the methyl group relaxation and the low temperature α -process are the same as obtained for the pure rubber. Accordingly the only free fitting parameters were the VTF and CD parameters for the high temperature α-process. For the latter process we obtained: bslow α =0.78, νslow α =2.24, Eatt, slow α =705 K, To, slow α =206 K. The temperature dependence of this process is also reported in Figure 3. At present no DS data are available on this sample, but we can anticipate that the detection of this process would be complicate as it falls in the temperature/frequency regime where DS spectra are dominated by conductivity, which masks other contributions.

Conclusion We have shown that a combined use of state of the art QENS and broadband dielectric spectroscopies can provide a useful insight into the relaxation processes occurring in polymer electrolytes.

In particular we exploited the wealth of information accessible from IFES, providing for the first time a detailed quantitative description of this kind of data sets.

Finally the use of IFES data allowed a qualitative as well as a quantitative detection of the dynamic heterogeneity that characterises the α-relaxation in PEs.

Acknowledgements We thank Dr. Y. Aihara (Yuasa Corp., Japan) for kindly providing the samples. During the experiment, we took advantage of the skilful technical assistance of Mr. T. Starc. A. T. also acknowledges fruitful discussions with Dr. V. Arrighi (Heriot-Watt University, UK). We acknowledge financial support from the European Community – Access to Research Infrastructure action of the Improving Human Potential Programme (HPRI-2001-00175) which funded the access to the FZJ facilities.

References [1] a) F. M. Gray, Polymer Electrolytes (Royal Society of Chemistry: Cambridge, 1997); b) J. R. MacCallum; C. A. Vincent, Polymer Electrolytes Reviews (Elsevier: New York, 1987; vol. I and II); c) Applications of Electroactive Polymers (B. Scrosati Ed., Chapman and Hall: London, 1993) [2] J. S. Higgins and H. C. Benoit, Polymers and Neutron Scattering (Oxford University Press, Oxford, 1993) [3] K. Hayamizu, Y. Aihara, W. S. Price, J. Chem. Phys 113, 4785 (2000) [4] www.fz-juelich.de/iff/wns_bss see also B. Alefeld, T. Springer, T. Heidemann, Nucl. Sci. and Engineering 110, 84 (1992) [5] H. H. Grapengeter, B. Alefeld, R. Kosfeld, Colloid and Polymer Sci., 265, 226 (1987) [6] see e.g. B. Frick, and L. J. Fetters, Macromolecules, 27, 974 (1994) [7] D. W. Davidson and R. H. Cole, J. Chem. Phys., 18, 1417 (1950) [8] A. Chahid, A. Alegria, J. Colmenero, Macromolecules, 27, 3282 (1994) [9] e.g. a) V. Arrighi, R. Ferguson, R. E. Lechner, M. Telling, A. Triolo, Physica B, 301, 35 (2001); b) R. Zorn, B. Frick, L. J. Fetters, J. Chem.

Phys. 116, 845 (2002); c) G. Allen, J. S. Higgins, Macromolecules, 10, 1006 (1977); d) R. Mukhopadhyay, A. Alegria, J. Colmenero and B. Frick, Macromolecules, 31, 3985 (1998) [10] see e.g. V. Arrighi and J. S. Higgins, J. Chem. Soc., Faraday Trans., 93, 1605 (1997) [11] C. Vachon, C. Labreche, A. Vallee, S. Besner, M. Dumontand, J. Prud’homme, Macromolecules 28, 5585 (1995) [12] a) R. Bergman, L. Borjesson, G. Fytas L. M. Torell, J. Non-Crystalline Solids 172-174, 839 (1994); b) R. Bergman, L. M. Torell, Solid State Ionics 85, 99 (1996) [13] A. Triolo et al., Physica B 301, 163 (2001); b) idem, Physica A 304 308 (2002)

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µ &N &SR NEWS NEUTRON PHYSICS LABORATORY OF NPI Rez PARTICIPATES IN TRANSNATIONAL ACCESS IN A JOINT PROGRAMME WITH NFL STUDSVIK Rez Neutron Physics Laboratory (NPL) is a part of Nuclear Physics Institute of the Czech Academy of Sciences, performing neutron physics experiments as well as to providing experimental facilities and research experience for external users. Research activities of NPL are concentrated at the medium power 10 MW (mean power) reactor LVR-15 which belongs to the Nuclear Research Institute, plc. (NRI, plc.) and it is operating on a commercial basis. The reactor operates on average about 170 days per year with a pattern of operating cycles of three weeks, each followed by one week for maintenance and instrumentation development.

The thermal neutron flux in the core is about 9x1013 n⋅cm2⋅s-1.

In total, NPL operates 8 instruments installed at 5 radial horizontal beam tubes (for experiments in nuclear physics, solid state physics and materials research) and two vertical irradiation channels (for neutron activation analysis) hired at NRI, plc.

For details see the Web page www.omega.ujf.cas.cz. The following instruments introduced in the text are offered for joint access program with NFL Studsvik. They are in other laboratories either overloaded by user demands (strain diffractometers) or are rarely provided (high resolution SANS, T-NDP and NAA). When using these instruments a considerable emphasis is placed on the provision of entire support including high quality software for data analysis, preliminary raw data elaboration and a permanent assistance of the responsible researcher. diffractometer TKSN-400 equipped with a bent Si single crystal monochromator and 3He position sensitive detector is dedicated to determination of internal strains in polycrystalline materials (contact

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lukas@ujf.cas.cz). The diffractometer uses advantages coming from focusing both in real and momentum space and yields very good resolution and luminosity. It is mainly used for mapping residual macrostrains, microstrain analysis and in situ tension/compression tests of samples in a large temperatures range above the room value.

SPN-100 multipurpose diffractometer equipped with a bent Si or Ge single crystal monochromator and 3He position sensitive detector (contact mikula@ujf.cas.cz or vrana@ujf.cas.cz). The diffractometer also uses advantages coming from focusing both in real and momentum space. It is mainly used for macrostrain scanning, neutron topography, special tasks of highresolution single-crystal and powder diffractometry in a short Q-range and Bragg diffraction optics.

DN-2 double-crystal diffractometer DN-2 is designed for the measurements of small-angle neutron scattering (SANS) in a high Q-resolution range. The fully asymmetric diffraction geometry of the bent Si analyser is employed to transfer the angular distribution of the scattered neutrons to the spatial distribution and to analyse the scattering curve by the 1-d PSD. The remote control of the curvatures of the monochromator and analyser crystals makes possible to tune the instrument resolution easily in the dQ range from 10-4 to 10-3 Å-1, according to the expected size of investigated inhomogeneities. It is mainly used for investigations of the inhomogeneities in the size range (0.05 ÷ 5) mm.

T- N D P thermal neutron depth profiling facility (contact vacik@ujf.cas.cz) consists of a large vacuum chamber, automatic target holders and several different data

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acquisition systems which can be used at the same time. T-NDP is used as a nuclear analytical technique for surface studies. It utilises the existence of isotopes of elements that produce prompt monoenergetic charged particles upon capture of thermal neutrons. From the energy loss spectra of emitted products the depth distributions of light elements can be reconstructed. T-NDP is mainly used for study of numerous problems in solid-state physics (diffusion, sputtering), material science (corrosion), electronics, optronics, life sciences etc.

NAA facility for neutron activation analysis is dedicated to both short- and long-time irradiations performed in vertical channels of the reactor which are located at the outskirts of the reactor core (contact kucera@ujf.cas.cz). For short-time irradiation (typically 0.5-3 min.) in PE-rabbits, a pneumatic system is available which connects the dry vertical channel behind a Be reflector to a measurement station outside the reactor hall. Long-time irradiation (several hours to several days) is carried out in sealed Al-cans in the wet vertical channels located in the Be reflector of the reactor core. The irradiated cans are transported to hot cells for disassembling and further analysis. NAA provides a highly accurate and low-level characterization of various materials by determining up to 40 elements.

The proposal procedure (see the Web page www.omega.ujf.cas.cz) is similar to that at NFL with no fixed deadlines. Everlapping membership of the referee panel will ensure consistent standars and effective use of the facilities.

Pavol Mikula NPI Rez, Czech Republic

µ & N & SR NEWS

MATERIALS INVESTIGATIONS USING MUONS AT ISIS AND PSI Europe is fortunate in having two world-class muon sources which provide European scientists with access to the muon technique for condensed matter investigations: ISIS, located at the Rutherford Appleton Laboratory in Oxfordshire, England, and PSI at Villigen, Switzerland. As sensitive, local magnetic probes, muons are used to study atomic-level structure and dynamics. The siting of both ISIS and PSI muon sources within neutron facilities, together with X-ray sources being available near-by, provides opportunities for researchers to exploit all three techniques in their investigations. Indeed, increasing numbers of researchers who use muons are also

regular neutron users, benefiting from the complementary information these techniques generate in many areas.

The Muon Technique At both ISIS and PSI, muons are produced by the passage of an energetic proton beam through a thin carbon target. The positive muon beams produced are naturally 100% spin polarised, and this polarisation is maintained as the muons are transported to the sample, implanted and thermalise. Muons have a mean lifetime of 2.2 µs after which time they decay, emitting a positron and two neutrinos. The decay positrons are

Fig. 1. Contour plot and projection of the time-average muon polarisation in silver (I) oxide, Ag2O as a function of applied magnetic field and temperature. From this, detailed information about the muon state electronic structure in this material can be deduced, informing by analogy on the states adopted by hydrogen.

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preferentially emitted in the instantaneous direction of the muon’s spin at time of decay – so that, by detecting the positrons coming from muon decays inside a sample, we are able to follow the behaviour of the muon polarisation as a function of time after implantation. This in turn tells us about the muons’ local magnetic environment and behaviour. The technique is known as µSR, which stands for muon spin rotation, relaxation and resonance (for an introductory review, see S.J. Blundell, Contemporary Physics, 40 (1999) 175).

Applications of the Technique Broadly speaking, applications of the muon technique fall into two categories – those where the muon is being used as a probe of its local environment, and those where the behaviour of the muon itself is the primary interest. In the former case, muon studies include a wide variety of magnetic systems, with muons being used to explore magnetic transitions, ordering and spin dynamics, and with the technique being sensitive to very small magnetic fields (down to 10-5 T) and appropriate for investigations where the magnetism is short-range, random, or dilute. In superconducting systems, as well as investigations of the atomic-level magnetism which may be found in many of these materials, muons can be used to explore the flux-line lattice generated when a field is applied to a type II material, and can be used to determine fundamental superconducting parameters such as the penetration depth, coherence length, superconducting carrier density, effective mass and pairing mechanism.

Muons are also used for investigations of ion mobility in battery cathode materials, charge carrier motion

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µ & N & SR NEWS

Fig. 2. The ISIS muon beamlines.

in conducting polymers and molecular dynamics.

Muons have a mass of one ninth that of the proton, and in some systems it is useful to think of the muon as a light proton isotope. Observation of muon behaviour then enables models to be built up of analogous hydrogen behaviour. This is particularly relevant to semiconductors, where muon studies have been invaluable in elucidating the charge states, lattice sites and dynamics of isolated hydrogen, including recently-discovered shallow-donor hydrogen states in wide band gap materials. Muons can also be used as proton analogues in proton conductors and hydrogen storage materials.

The ISIS and PSI Muon Facilities The ISIS and PSI facilities are complementary in terms of the types of measurements which can be performed owing to the different nature

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Fig. 3. The DEVA muon spectrometer at ISIS, during its use for radiofrequency muon spin resonance experiments.

of muon production at each. A pulsed beam facility such as ISIS is very suited to studies requiring measurement to long times after muon implantation and those entailing application of a pulsed stimulus to the implanted muons or sample. PSI, where muons are produced continuously, is particularly suitable for studies where the muon polarisation changes rapidly with time after muon implantation. ISIS has four muon instruments, together with associated sample environment equipment spanning temperatures of 25 mK – 1000 K and fields of 0 – 0.45 T, together with facilities for gas and liquid handling and a variety of pulsed environments (e.g. RF radiation, E- and B-fields, current, light).

PSI has six instruments for temperatures 10 mK – 900 K, fields 0 – 5 T, and pressures up to 14 kbar; the unique low-energy muon source (tunable muon energy 0.5 – 30 keV) allows depth-resolved investigation

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of near surfaceregions, thin films, layered structures and interfaces on a nm scale. Both facilities welcome new users, and both have EC Access contracts providing funding for European researchers under Framework Programme 6 – further details can be found from their web sites www.isis.rl.ac.uk/muons/ and lmu.web.psi.ch, together with the European neutron and muon portal http://www.muon-eu.net/.

Philip King ISIS Muon Facility, philip.king@rl.ac.uk Dierk Herlach PSI Muon Facility, dierk.herlach@psi.ch)

µ & N & SR NEWS

ILL & ESRF CONTRIBUTION Common Section PSB - The Partnership for Structural Biology Takes Shape The PSB is a unique integrated programme and resource pool in structural genomics and proteomics. It includes the ESRF, Europe’s foremost synchrotron X-ray source, the ILL, the world’s leading neutron source, the Grenoble Outstation of the European Molecular Biology Laboratory, and the IBS, one of France’s premier

structural biology institutes. The four partners bring together their expertise in state-of-the-art structural and molecular biology in order to tackle fundamental research problems related to human health.

More than a year after its creation by the four research institutes in Grenoble (France) PSB is becoming a reality by uniting the activities of the four partners in a joint building.

Planning permission for the dedicated laboratory building was obtained and ground breaking will

take place in June this year. Scientific collaboration is also taking shape.

The PSB project advances. “Everything is set”, said Stephen Cusack, director of the EMBL Grenoble outstation. Indeed, the ESRF and ILL Councils late in 2003 gave the green light for the construction and equipment budget for a new laboratory complex located next to EMBL premises on the international site in Grenoble. The building will have 1800 m 2 of usable surface area. Its construction is due to start in June 2004 and should be finished 15 months later. The laboratory complex will also host the IVMS, the molecular virology institute of the Grenoble Université Joseph Fourier. The director of the ESRF, Bill Stirling, explains that “the PSB is currently one of the ESRF’s major scientific projects. We hope that the combination of skills of the four partner institutes will make the PSB a world centre for research in Structural Biology”.

In the context of the PSB, the ESRF has constructed a new, state-of-theart, X-ray beamline, which is already partly operational, and the ILL has set up a unique laboratory for the deuteration of proteins, which is already available to user groups. The Partnership will also include highthroughput protein expression and crystallisation facilities as well as facilities for protein characterisation.

Gemini: A new state-of-the-art beamline inaugurated at the ESRF The first end-stations of the new ID23 beamline at the ESRF is operational. Associated with the PSB scientific programme, it is designed to achieve high-throughput measurements for macromolecular crystallography in an automatic, industrialised and easily usable environment. Modern macromolecular crys-

Fig. 1. The new PSB building, which is being constructed

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allowing researches to solve structures from the smallest and most exciting samples.

Fig. 2. Didier Nurizzo (left), scientist in charge on ID23-1, discusses with Martin Noble (right), head of the first team of users on this beamline, from the University of Oxford.

tallography experiments take under one hour to complete compared to an entire day or days a few years ago. This turnover is expected to increase with the automation of the beamlines being developed at the ESRF and EMBL. By the end of 2004, the first ID23 station will be equipped with a robotic sample changer allowing users to rapidly screen and assess their projects.

Protein crystal samples are becoming ever smaller and difficult to manipulate, with today’s samples typically around 50 microns in size.

ID23-1 will use a high de-magnification ratio of 1:4.5 in order to obtain a small focused beam at the sample position. The first official users on the beamline came from the University of Oxford in April with the aim of studying samples of proteins.

“This beamline is a fantastic resource, that’s why we brought our most challenging samples, of 10 microns”, explains Martin Noble, head of the team. The second end-station of ID23 is under design now and is really targeting the small crystals of protein complexes expected in the future. A custom made undulator Xray source and focusing system will generate an intense micro-focus Xray beam of 5 to 10 microns in size

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Deuteration Laboratory The deuteration, partial or full, of biological molecules, proteins, nucleic acids, lipids, sugars, is essential to exploit fully the techniques of neutron scattering. As part of it’s strategy for the expansion of the life sciences program in neutron scattering the ILL, in collaboration with EMBL, has set up a laboratory for the deuteration of biological molecules.

A molecular biologist experienced in macromolecular deuteration has been appointed and a well-equipped laboratory provided.

Access to the deuteration laboratory will be via proposals that will be peer-reviewed by a panel of international experts nominated by the ILL Scientific Council in collaboration with the EMBL. Once completed, proposals should be sent, as an electronic attachment, to the ILL Scien-

Fig. 3.

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tific Coordination Office (sco@ill.fr).

Templates are available on the ILL web site: (http://www.ill.fr/pages/scence/U ser/UProposals.htm).

FaME 38 - Facility for Materials Engineering FaME38 provides support to enable European materials engineers to make the best use of the advanced neutron and synchrotron X-ray scientific facilities at ILL-ESRF, which are respectively the leading European centres for research using neutron and synchrotron X-ray beams.

FaME38 supports a variety of materials engineering applications. New users are helped to plan, undertake and evaluate experiments, and are assisted with data collection, processing and analysis. Industrial users can additionally be provided with a full measurement and data analysis service if required. For any queries, contact the FaME38 team (FaME38@ill.fr)!

µ & N & SR NEWS

Italian senators visit the ESRF-ILL On Monday 8 March, the ILL and ESRF welcomed a delegation of Italian Senators (Commissione Cultura).

The purpose of the visit was a better knowledge of the two large scale facilities of our region. The invited senators were M. Asciutti (President of the Commission), M. Brignone, M. Compagna, M. Favaro, M. Monticone et Mrs Acciarini; they were accompanied by their counsellor, M. Fucito. After a general presentation of the two facilities, they visited the Italian CRGs at ILL (BRISP and IN13) and at the ESRF (GILDA and GRAAL). They were accompanied all along their visit by the representatives and instrument responsibles of INFM, Istituto nazionale per laFisica della Materia, which is the Italian Institute financing the ILL (3.5%) and ESRF (16%). The senators were impressed both by the high scientific level of the ILL and the ESRF and the importance of the Italian presence in the two facilities (22 Italians at the ILL, 40 at the ESRF). After the evening buffet they had the possibility of meeting the Italian staff on site before their departure and to congratulate them for their enthusiasm and their professionalism.

ESRF Section Record Requests for Beam Time Following the User Meeting in February, potential users submitted a record number of 923 applications for beam time for the March 1st deadline. This represents an increase of some 23% over the number of projects submitted in September 2003.

The distribution of proposals across major scientific areas during this review round, compared with September 2003, is shown in the figure 3.

Nine Review Committees of experts in a range of scientific domains met in parallel at the ESRF in

April; they assessed the applications for their scientific quality, and recommended projects to be scheduled on beamlines during the second half of 2004.

For information about the ESRF, have a look at www.esrf.fr, or call +33 476 88 20 00.

ILL Section The following workshops will be organised at the ILL next Autumn:

ESRF-ILL Workshop on Engineering Applications of Neutrons and Synchrotron Radiation (13-14 September) It is organised by the new joint ILLESRF Facility for Materials Engineering - FaME38. The aim of the workshop is to increase the awareness of the European materials science community to the materials characterisation techniques available at the large-scale neutron and synchrotron X-ray facilities. These techniques have enormous potential for research, diagnostic and development applications in materials science and engineering. Workgroup sessions will encourage collaborations, new projects and networks.

Web site: http://www.ill.fr/FaME38/workshop.htm

Neutrons & Numerical Methods (15-18 September) The purpose of this workshop is three-fold; to expose experimentalists and theoreticians to the added value of numerical modelling in research, to assemble and assess the most recent developments in neutron scattering and numerical modelling and to consider the role of simulations in the future. Most contributions are expected in the fields of soft condensed matter, chemical physics and materials, including magnetism. The workshop will be

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open to experienced simulators and to experimentalists and theoreticians wanting to learn about simulations. Scientists using X-rays (for example at the neighbouring ESRF facility) are also encouraged to participate since, for example, the fomalism for inelastic scattering is essentially the same as for neutrons. A one day “school” will precede the workshop.

Web site: http://whisky.ill.fr/Events/N2M2/ index.html

International workshop on Medium Pressure Advances for Neutron Scattering (20-23 October) The workshop will be focussed on the scientific and technical advances of neutron scattering at medium pressures, i.e. up to 3500 MPa (35 kbar). By allowing large sample environments such as gas or liquid pressure cells, neutron scattering gives a very direct access to precise information (e.g. crystal structure with light elements, magnetic ordering, excitations) necessary in numerous scientific areas where pressure is a crucial control parameter. The meeting will be inter-disciplinary, covering the fields of Physics, Chemistry, Materials Science, Geophysics and Bioscience. In all these areas, the use of pressure as a control parameter is gaining importance. In addition to the scientific program, the progress and development of new pressure techniques will be an important part of the workshop. Special emphasis will be put on the needs of the neutron user community, future developments and new perspectives.

Web site: http://www.ill.fr/Events/MPN/M Pa4neut.html

News from the ILL Scientific Council Overall, the subcommittees allocated

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1270 days on all instruments (there were 50 days available for allocation this round). This represents 236 accepted proposals out of 388 submitted. Of the 25 Italian proposals submitted, 12 received beam time with a total of 45 days, corresponding to about 3.5% of the total beam time available.

The next Scientific Council with its subcommittee meetings will be from 2 to 4 November 2004.

ILL Call for Proposals The deadline for proposal submission is Tuesday, 21 September 2004, midnight (European time).

Proposal submission is only possible electronically. Electronic Proposal Submission (EPS) is possible via our Visitors’ Club (http://www.ill.fr, Users & Science, Visitors’ Club, or directly at http://vitraill.ill.fr/cv/ ), once you have logged in with your personal username and password.

The detailed guide-lines for the submission of a proposal at the ILL can be found on the ILL web site: www.ill.fr, Users & Science, User Information, Proposal Submission, Standard Submission.

The web system will be operational from 1 July 2004, and it will be closed on 21 September, at midnight (European time). You will get full support in case of computing hitches. If you have any difficulties at all, please contact our web-support ( club@ill.fr ).

For any further queries, please contact SCO: ILL-SCO, 6 rue Jules Horowitz BP 156, F-38042 Grenoble Cedex 9 phone: +33 4 76 20 70 82, fax: +33 4 76 48 39 06 email: sco@ill.fr, http://www.ill.fr

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Instruments available The following instruments will be available for the forthcoming round: • powder diffractometers: D1A † , D1B*, D2B, D20 • liquids diffractometer: D4 • polarised neutron diffractometers: D3, D23* • single-crystal diffractometers: D9, D10, D15*, VIVALDI • large scale structure diffractometers: D19, DB21, LADI • small-angle scattering: D11, D22 • reflectometers: ADAM*, D17 • small momentum-transfer diffractometer: D16 • diffuse-scattering spectrometer: D7 • three-axis spectrometers: IN1, IN3, IN8, IN12*, IN14, IN20, IN22* • time-of-flight spectrometers: IN4, IN5, IN6 • backscattering and spin-echo spectrometers: IN10, IN11, IN13*, IN15, IN16 • nuclear-physics instruments: PN1, PN3 • fundamental-physics instruments: PF1B, PF2 † D1A is shared between powder diffraction (D1A PWD) and strain scanner applications (D1A STR). * Instruments marked with an asterisk are CRG instruments, where a smaller amount of beam time is available than on ILL-funded instruments, but we encourage such applications.

You will find details of the instruments on the web, http://www.ill.fr /index_sc.html.

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Scheduling period Those proposals accepted at the next round, will be scheduled during the FIRST TWO CYCES in 2005. You are probably already aware of the fact that - due to reinforcement work of the reactor structure - the ILL has reduced the number of reactor cycles from 4.5 down to 3 cycles per year until 2006.

Reactor Cycles for 2005 (provisional): Cycle n° 140

Cycle n° 141

Cycle n° 142

From

08/02/2005

To

30/03/2005

From

12/04/2005

To

01/06/2005

From

14/06/2005

To

03/08/2005

Start-ups and shut downs are planned at 8:30 am.

Giovanna Cicognani (ILL Scientific Co-ordinator) Montserrat Capellas Espuny (ESRF Press Officer)

µ & N & RS NEWS

THE GEESTHACHT NEUTRON FACILITY GENF Abstract With the beginning of the European framework program 6 (FP6) the Geesthacht Neutron Facility (GeNF) has been awarded an access-grant within the new NMI3 consortium further opening up its neutron instrumentation for a wide international user community. The longstanding experience in the operation of the research reactor for user driven science in combination with a strong in-house research will now be of benefit for an even larger group of scientists and industry.

Fig. 1. GKSS Research Centre Geesthacht

Main Text The Geesthacht Neutron Facility (GeNF, http://genf.gkss.de) is operated as part of the Geesthacht Neutron and Synchrotron Scattering Facility (GeNeSyS) by the GKSS Research Centre Geesthacht (Figure 1) near Hamburg, Germany. The neutron source of GeNF is the 5 MW swimming pool type reactor FRG-1 which provides an unperturbed flux of 1.4 × 1014 neutrons/(cm2s). With an average of 250 days of operation per year the FRG-1 provides the highest availability of all German research reactors.

The instrumentation of GeNF (Figure 2) has been strongly influenced by in house research focused dominantly on engineering materials science problems, on chemical and biological research as well as on magnetism. It is complimentary to that at other research reactors since it is unique worldwide in its concentration of six of the instruments on engineering materials research [one small-angle machine (SANS-2), one ultra small angle machine (DCD), two strain scanners (ARES, FSS), a neutron radiography facility (GENRA-3) and one texture diffractometer (TEX-2)]. The second focus is on instruments for

the investigation of soft matter such as biological structures, polymers, and colloids [another small angle machine (SANS-1) and two reflectometers (NeRO and PNR)] which make use of the strong scattering contrast of neutrons for hydrogen and deuterium dominating soft matter. The third focus is on the investigation of magnetic materials. The two small angle machines and both reflectometers (PNR, NeRO) have polarized beam capability, opening them up also for research on magnetic structures. This is a traditional strength of neutrons frequently demanded by external users.

Complementary to neutron scattering experiments GKSS also operates facilities at the synchrotron laboratory HASYLAB at DESY, Hamburg. If desired access can be given to these instruments where strain scanning and texture investigations with high energy X-rays (Liss et al. 2003) as well as microtomography can be performed.

Unlike at other neutron facilities applications for beam time can be submitted continuously at GeNF (http://genf.gkss.de, electronic submission) and will be reviewed with-

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in four to six weeks on receipt. This allows to react very fast and flexibly on user demands and provides the possibility e.g. to thesis students to gain as much training as possible.

Furthermore, users who plan a long term project (such as a Ph. D. thesis) can submit project proposals which cover a series of measurements over up to three years. Where appropriate, users can get coordinated sequential beam time on a number of instruments. A speciality of our facility is the support of not well trained or completely new users and -last but not least- of industrial customers which make use of nearly a third of our beamtime. The local contacts in general are physicists or chemists with their own research program specialised on one of the GKSS research topics. These are mainly: • materials science: correlation between macroscopic (e.g. mechanical, magnetic) properties of materials and parts and their structure down to the atomic scale. Prominent examples are residual stress analysis (Staron et al. 2002), quantitative texture analysis (Brockmeier et al. 2002; Günther et al.

2002), precipitates, clusters and

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bubbles (Staron et al. 2003; Bellmann et al., 2002; Nadutov et al.

2002; Staron and Kampmann, 2000), structure of the interfaces in thin film systems, magnetic structures (Zabel and Schreyer, 1998; Schreyer et al. 2000) • soft matter research: biological macromolecules (Willumeit et al.

2001a; Willumeit et al. 2001b; Blaha et al. 2003), colloids / microemulsions / nano-particles and polymers (He et al. 2002; Garamus 2003; Garamus et al. 2003).

In summary GeNF not only provides the users with high quality instrumentation but also with adequate scientific support on high international standards. We are looking forward to be of service for you!

Reference List - Bellmann, D., Clemens, H. and Banhart, J.: USANS investigation of early stages of metal foam formation. J. Appl. Phys. A, 74 (2002) s1136-s1138.

- Blaha, G., Wilson, D.N., Stoller, G., Fischer, G., Willumeit, R. and Nierhaus, K.H.: Localization of the trigger factor binding site on the ribosomal 50S subunit, JMB 326 (2003) 887-897.

- Brokmeier, H.-G., Singer, W. and Kaiser, H.: Neutron diffraction - a tool to optimize processing of niobium tubes. Appl. Phys. A. Material Science & Processing 74 (2002) 1704-1706.

- Garamus, V.M.: Formation of Mixed Micelles in Salt-Free Aqueous Solutions of Sodium Dodecyl Sulfate and C12E6, Langmuir 19 (2003 ) 7214-7218.

- Garamus, V.M., Pedersen, J.S., Maeda, H. and Schurtenberger, P.: Scattering from short stiff cylindrical micelles formed by full-ionized TDAO in NaCl/water solutions, Langmuir 19 (2003) 3656-3665.

- Günther, A., Brokmeier, H.-G., Petrovsky, E., Siemes, H., Helming, K. and Quade, H.: Mineral preferred orientation and magnetic properties as indicators of varying strain conditions in naturally deformed iron ore. Appl.

Phys. A. Material Science & Processing 74 (2002) 1080-1082.

- He, L.-Z., Garamus, V., Funari, S., Malfois, M., Willumeit, R. and Niemeyer, B.: Comparison of small angle scattering methods for the structure analysis of octyl-b-maltopyranoside forming nanostructured aggregates, J. Phys.

Chem. B 106 (2002) 7596-7604.

- Liss, K.D., Bartels, A., Schreyer, A. and Clemens, H.: High-energy X-rays: A tool for advanced bulk investigations in materials science and physics, Textures and Microstructures 35 (2003) 219-252.

- Nadutov, V.M., Garamus, V.M. and Islamov, A.Kh.: Small-Angle Neutron Scattering and the Mössbauer Effect in Nitrogen Austenite, Physics of the Solid State 44 (2002) 686-691.

- Schreyer, A., Schmitte, T., Siebrecht, R., Bödeker, P., Zabel, H., Lee, S. H., Erwin, R.W., Kwo, J., Hong, M. and Majkrzak, C.F.: Neutron scattering on magnetic thin films: Pushing the limits, J. Appl. Phys. 87 (2000) 5443-5448.

- Staron, P. and Kampmann, R.: Early-stage de-

-

-

-

-

-

composition kinetics in Ni-Al alloys - I. Small and wide-angle neutron scattering investigation on Ni-13 at.% Al and clusterdynamic modelling. Acta Mater 48 (3) (2000) 701-712.

Staron, P., Koçak, M. and Williams, S.: Residual stresses in friction stir welded Al sheets.

Appl. Phys. A 74 (2002) s1161-s1162.

Staron, P., Jamnig, B., Leitner, H., Ebner, R. and Clemens, H.: Small-angle neutron scattering analysis of the precipitation behaviour in a maraging steel, J. Appl. Cryst. 36 (2003) 415-419.

Willumeit, R., Forthmann, S., Beckmann, J., Diedrich, G., Ratering, R., Stuhrmann, H.B. and Nierhaus, K.H.: In situ structure determination of the protein L2 in the 50S subunit and the 70S E. coli ribosome, J. Mol. Biol.

305(1) (2001a) 167-177.

Willumeit, R., Diedrich, G., Forthmann, S., Beckmann, J., May, R.P., Stuhrmann, H.B. and Nierhaus, K.H.: Mapping proteins of the 50S Subunit from E.coli ribosomes, BBA 1520 (2001b) 7-20.

Zabel, H. and Schreyer, A.: Polarized Neutron Reflection: Revealing Spin Structures in Nanostructured Layers, Neutron News 9 (1998) 18-23.

Regine Willumeit* and Andreas Schreyer** GKSS Research Centre Geesthacht, Max-Planck-Str.1, 21502 Geesthacht, Germany *Tel: +49(0)4152 871291, email: willumeit@gkss.de **Tel: +49(0)4152 871254, email: schreyer@gkss.de

Fig. 2. Instrumentation at GeNF. The neutron source (CNS) feeds about half of the experiments with cold neutrons.

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MEETING AND REPORTS

Giornate Didattiche “Dinamica dei sistemi molecolari complessi” e Congresso Annuale 2004 5-7 e 8-9 Luglio 2004 Hotel Monte Conero Sirolo (AN)

Le Giornate Didattiche della SISN (Società Italiana di Spettroscopia Neutronica) sono una nuova iniziativa rivolta essenzialmente a studenti, dottorandi e borsisti interessati ad acquisire i primi elementi di spettroscopia neutronica con lo scopo non solo di comprenderne vantaggi e potenzialità, ma anche di applicarla praticamente alla loro ricerca.

Programma delle Giornate Didattiche Elementi Teorici • Introduzione generale alla diffusione neutronica (Prof. F. Sacchetti, Università di Perugia) • Sorgenti e strumentazione (Dr. M. Zoppi, IFAC - CNR) • Spettroscopia vibrazionale: neutroni, Raman ed IR (Prof. S. Magazù, Università di Messina) • Diffusione anelastica coerente: neutroni, luce, raggi X (Dr. U. Bafile, IFAC-CNR) • Diffusione quasielastica e spettroscopie di rilassamento (Prof. A. Deriu, Università di Parma) • Simulazioni di dinamica molecolare: dalle molecole alle macromolecole (Dr. S. Melchionna, Università di Roma La Sapienza) Attività Sperimentale Italiana • Diffusione anelastica coerente: BRISP (Dr. F. Formisano, OGG - INFM) • Diffusione elastica e quasielastica: IN13 (Dr. F. Natali, OGG - INFM) • Spettroscopia vibrazionale: TOSCA (Dr. D. Colognesi, IFAC - CNR) • Spettroscopia anelastica: VESUVIO (Dr. R. Senesi, Università di Roma “Tor Vergata” e INFN) Seminari Specialistici • Idruri complessi (Prof. A. Albinati, Università di Milano) • Dinamica di calixareni e composti “caged” (Prof. R. Caciuffo, Università di Ancona) • Relazione struttura-dinamica-funzione nelle biomolecole (Prof. R. Rolandi, Università di Genova) Sessioni interattive • Elaborazione di dati sperimentali (ad es. trasformazioni ToF-energia, sottrazione della cella ecc.) mediante programmi interattivi (a cura del Dr. A. Paciaroni, Università di Perugia)

CONGRESSO SISN 2004

8 Luglio Tre relazioni su invito (60 min.)

Otto comunicazioni orali (30 min.)

Sessione poster

9 Luglio Una relazione su invito (60 min.)

Assemblea SISN Premiazione dei poster

Comitato Scientifico: F. Aliotta, U. Bafile, F. Barocchi, F. Carsughi, D. Colognesi, A. Deriu, A. Paciaroni Termine per le iscrizioni alle Giornate Didattiche e per la Presentazione di Abstract per il Congresso: 30 MAGGIO 2004 Segreteria delle Giornate Didatttiche e del Congresso: Dr. D. Fermi, Unità INFM di Parma Parco Area delle Scienze 7/A - I-43100 Parma - Tel: 0521 905197 o 905565 - Fax: 0521 906022 - e-mail: Daniela.Fermi@fis.unipr.it

Con il patrocinio dell’INFM-CNR Società Italiana di Spettroscopia Neutronica - www.sisn.it

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CALL FOR PROPOSAL

Call for proposals for

Call for proposals for

Neutron Sources

Synchrotron Radiation Sources

BENSC

ALS

Deadlines for next call are: 15 September 2004 and 15 March 2005

Deadlines for next call are: 15 July 2004 and 15 September 2004 (cristallografia macromolecolare), 7 July 2004 (general users)

ILL Deadline for next call is: 21 September 2004

BESSY Deadlines for next call are: 15 August 2004 and 15 February 2005

ISIS Deadlines for next call are: 16 October 2004 and 16 April 2005

DARESBURY Deadlines for next call are: 31 October 2004 and 30 April 2005

LLB-ORPHEE-SACLAY Deadline for next call is: 1 October 2004

ELETTRA Deadlines for next call are: 31 August 2004 and 28 February 2005

SINQ Deadline for next call is: 15 November 2004

ESRF Deadlines for next call are: 1 September 2004 and 1 March 2005

FZ Juelich Deadline for next call is: 8 November 2004

GILDA (quota italiana) Deadlines for next call are: 1 November 2004 and 1 May 2005

HASYLAB (new projects) Deadlines for next call are: 1 September 2004 and 1 March 2005

MAX-LAB Deadline for next call is: February 2005

NSLS Deadlines for next call are: 30 September 2004, 31 January and 31 May 2005

SLS Deadlines for next call are: 15 October 2004, 15 February 2005 and 15 June 2005 (cristallografia) 15 September 2004 and 15 March 2005 (general users)

Vol. 9 n. 2 July 2004

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CALENDAR

June 28 - 30, 2004

WARWICK UNIVERSITY, UK

Neutron and Muon Users Meeting (NMUM 2004) with the New Perspectives in Neutron and Muon Science workshop (NPNMS 2004) C.R.Owen@cclrc.ac.uk +44 1235 446882 +44 1235 445147 Corporate Development, Directorate CCLRC Rutherford Appleton Laboratory Chilton, Didcot Oxfordshire, OX11 0QX - UK

July 26 - 30, 2004

5th International Topical Meeting on Neutron Radiography (IT-MNR-5) Contact: Thomas Buecherl Tel: +49 (0) 89 289-14328 Fax: +49 (0) 89 289-14347 E-mail: itmnr5@isnr.de URL: http://www.isnr.de

Aug 2 - 6, 2004

July 11 - 16, 2004

METZ, FRANCE

12th International Conference on Liquid and Amorphous Metals (LAM12) Institut de Physique 1, Bd Arago - 57078 Metz Cedex 3, France Fax : + 33 3 87 31 58 84 or + 33 3 87 31 58 01 Conference e-mail :lam12@sciences.univ-metz.fr Contact: Dr. Monique Calvo-Dahlborg, LSG2M CNRSUMR 7584, Ecole des Mines, Parc de Saurupt, 54042 Nancy Cedex, France E-mail: lam12@mines.inpl-nancy.fr URL: http://www.mines.inpl-nancy.fr/~lam12/

PRAGUE, CZECH REPUBLIC

20th General Conference of the Condensed Matter Division (EPS) URL: http://cmd.karlov.mff.cuni.cz/CMD/

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DENVER, COLORADO, USA

The International Symposium on Optical Science and Technology Spie’s 49TH Annual meeting.

Advances in Computational Methods for X-Ray and Neutron Optics (AM304) Colorado Convention Center Telephone: +1 360/676-3290 | Fax +1 360/647-1445 | Email: spie@spie.org http://spie.org/conferences/programs/04/am/ Contact: Manuel Sanchez del Rio E-mail: srio@esrf.fr URL: http://spie.org/Conferences/Calls/04/am/ conferences/index.cfm?fuseaction=AM304

Sep 1 - 4, 2004 July 19 - 23, 2004

GARCHING, GERMANY

ARCACHON, FRANCE

7th International Conference on Quasi-Elastic Neutron Scattering (QENS 2004) Contact: A. Desmedt and F. Guillaume Fax: +33 (0) 540-008-402 E-mail: info@qens2004.org URL: http://www.qens2004.org

CALENDAR

Sep 5 - 18, 2004

GRENOBLE CEDEX, FRANCE

Workshop Neutrons and Numerical Methods 2 Organisers: M. Johnson, M. Gonzalez, D. Kearley, T. Mounir Workshop Secretaries: A. Mader, I. Volino Institut Laue-Langevin, B.P. 156, F-38042 Grenoble, France Tel.: +33 (0)4 76.20.75.25, Fax: +33 (0)4.76.20.76.88, E-mail: n2m2@ill.fr - http://www.ill.fr/Events/N2M2

Sep 19 - 25, 2004

International School and Symposium on Physics in Materials Science (ISSPMS’2004) Contact: Prof. Andrzej Czachor Tel: +48 22 7180118 E-mail: ISSPMS2004@ipj.gov.pl URL: http://www.ipj.gov.pl/common/ISSPMS2004/

Oct 20 - 23, 2004 Sep 13 - 14, 2004

GRENOBLE, FRANCE

Engineering applications of neutrons and synchrotron radiation,.

Joint FaME38 - ILL - ESRF workshop FaME38 at ILL-ESRF 6, rue Jules Horowitz , BP 156 38042 Grenoble CEDEX 9-France Tel.: +33-476-20-7944 Fax.: +33-476-20-7943 User Centre phone: +33-476-20-7941; Email: FaME38@ill.fr

USTRON-JASZOWIEC, POLAND

GRENOBLE CEDEX, FRANCE

Workshop at ILL: “International Workshop on Medium Pressure Advanced for Neutron Scattering” http://www.ill.fr/Events/MPN/MPa4neut.html

Nov 27 - Dec 2, 2005

SYDNEY, AUSTRALIA

International Conference on Neutron Scattering (ICNS 2005) Contact: Brendan Kennedy E-mail: B.Kennedy@chem.usyd.edu.au URL: http://www.sct.gu.edu.au/icns2005/ http://www.icns2005.org/announce.html

For information on advertising rates, media packs and inserts, and Conference Announcements please contact: Ms. Desy Catena Tel: +39 6 72594100 - Fax: +39 6 2023507 E-mail: desy.catena@uniroma2.it

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FACILITIES

LUCE DI SINCROTRONE SYNCHROTRON SOURCES WWW SERVERS IN THE WORLD (http://www.esrf.fr/navigate/synchrotrons.html) ALS Advanced Light Source Berkeley Lab, 1 Cyclotron Rd, MS6R2100, Berkeley, CA 94720 tel: +1 510.486.7745 fax: +1 510.486.4773 http://www-als.lbl.gov/ Tipo: D Status: O

ANKA Forschungszentrum Karlsruhe Institut für Synchrotronstrahlung Hermann-von-Helmholtz-Platz 1 76344 Eggenstein-Leopoldshafen, Germany tel: +49 (0)7247 / 82-6071 fax: +49-(0)7247 / 82-6172 http://hikwww1.fzk.de/iss/

APS Advanced Photon Source Bldg 360, Argonne Nat. Lab. 9700 S. Cass Avenue, Argonne, Il 60439, USA tel:+1 708 252 5089 fax: +1 708 252 3222 http://epics.aps.anl.gov/welcome.html Tipo: D Status: C

ASTRID ISA, Univ. of Aarhus, Ny Munkegade, DK-8000 Aarhus, Denmark tel: +45 61 28899 fax: +45 61 20740 http://www.aau.dk/uk/nat/isa Tipo: PD Status: O

BESSY Berliner Elektronen-speicherring Gessell.für Synchrotron-strahlung mbH BESSY GmbH, Albert-Einstein-Str.15, 12489 Berlin, Germany, tel +49 (0)30 6392-2999 fax +49 (0)30 6392-2990 http://www.bessy.de Tipo: D Status: O

BSRL Beijing Synchrotron Radiation Lab. Inst. of High Energy Physics, 19 Yucuan Rd.PO Box 918, Beijing 100039, PR China tel: +86 1 8213344 fax: +86 1 8213374 http://solar.rtd.utk.edu/~china/ins/IHEP/bsrf/bsrf.html Tipo: PD Status: O

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CAMD Center Advanced Microstructures & Devices Louisiana State University, Center for Advanced Microstructures & Devices, 6980 Jefferson Hwy., Baton Rouge, LA 70806 tel: (225) 578-8887 fax. (225) 578-6954 Fax http://www.camd.lsu.edu/ Tipo: D Status: O

CHESS Cornell High Energy Synchr. Radiation Source Wilson Lab., Cornell University Ithaca, NY 14853, USA tel: +1 607 255 7163 fax: +1 607 255 9001 http://www.tn.cornell.edu/ Tipo: PD Status: O

CLS Canadian Light Source, University of Saskatchewan, 101 Perimeter Road, Saskatoon, SK., Canada. S7N 0X4 http://www.cls.usask.ca/ Tipo:D status:C

DAFNE INFN Laboratori Nazionali di Frascati, P.O. Box 13, I-00044 Frascati (Rome), Italy tel: +39 6 9403 1 fax: +39 6 9403304 http://www.lnf.infn.it/ Tipo:P Status: C

DELTA Universität Dortmund,Emil Figge Str 74b, 44221 Dortmund, Germany tel: +49 231 7555383 fax: +49 231 7555398 http://prian.physik.uni-dortmund.de/ Tipo: P Status: C

DIAMOND Diamond Light Source Ltd, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX http://www.diamond.ac.uk/ Tipo:D status:C

FACILITIES

ELETTRA Sincrotrone Trieste, Padriciano 99, 34012 Trieste, Italy tel: +39 40 37581 fax: +39 40 226338 http://www.elettra.trieste.it Tipo: D Status: O

Kurchatov Kurchatov Inst. of Atomic Energy, SR Center, Kurchatov Square, Moscow 123182, Russia tel: +7 95 1964546 Tipo: D Status: O/C

ELSA Electron Stretcher and Accelerator Nußalle 12, D-5300 Bonn-1, Germany tel:+49 288 732796 fax: +49 288 737869 http://elsar1.physik.uni-bonn.de/elsahome.html Tipo: PD Status: O

LNLS Laboratorio Nacional Luz Sincrotron CP 6192, 13081 Campinas, SP Brazil tel.: (+55) 0xx19 3287.4520 fax: (+55) 0xx19 3287.4632 http://www.lnls.br/ Tipo: D Status: C

ESRF European Synchrotron Radiation Lab. BP 220, F-38043 Grenoble, France tel: +33 476 882000 fax: +33 476 882020 http://www.esrf.fr/ Tipo: D Status: O

LURE Bât 209-D, 91405 Orsay ,France tel: +33 1 64468014; fax: +33 1 64464148 http://www.lure.u-psud.fr Tipo: D Status: O

EUTERPE Cyclotron Lab.,Eindhoven Univ. of Technol, P.O.Box 513, 5600 MB Eindhoven, The Netherlands tel: +31 40 474048 fax: +31 40 438060 Tipo: PD Status: C

MAX-Lab Box 118, University of Lund, S-22100 Lund, Sweden tel: +46 46 109697 fax: +46 46 104710 http://www.maxlab.lu.se/ Tipo: D Status: O

HASYLAB Notkestrasse 85, D-2000, Hamburg 52, Germany tel: +49 40 89982304 fax: +49 40 89982787 http://www-hasylab.desy.de/ Tipo: D Status: O

NSLS National Synchrotron Light Source Bldg. 725, Brookhaven Nat. Lab., Upton, NY 11973, USA tel: +1 516 282 2297 fax: +1 516 282 4745 http://www.nsls.bnl.gov/ Tipo: D Status: O

INDUS Center for Advanced Technology, Rajendra Nagar, Indore 452012, India tel: +91 731 64626 http://www.ee.ualberta.ca/~naik/accind1.html Tipo: D Status: C

NSRL National Synchrotron Radiation Lab. USTC, Hefei, Anhui 230029, PR China tel +86-551-5132231,3602034 fax +86-551-5141078 http://www.nsrl.ustc.edu.cn/en/enhome.html Tipo: D Status: O

KEK Photon Factory Nat. Lab. for High Energy Physics, 1-1, Oho, Tsukuba-shi Ibaraki-ken, 305 Japan tel: +81 298 641171 fax: +81 298 642801 http://www.kek.jp/ Tipo: D Status: O

Pohang Pohang Inst. for Science & Technol., P.O. Box 125 Pohang, Korea 790600 tel: +82 562 792696 fax: +82 562 794499 http://pal.postech.ac.kr/english.html Tipo: D Status: C

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FACILITIES

Siberian SR Center Lavrentyev Ave 11, 630090 Novosibirsk, Russia tel: +7 383 2 356031 fax: +7 383 2 352163 http://ssrc.inp.nsk.su/english/load.pl?right=general.html Tipo: D Status: O

SLS Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI http://sls.web.psi.ch/view.php/about/index.html Tipo: D Status: O

SPring-8 2-28-8 Hon-komagome, Bunkyo-ku ,Tokyo 113, Japan tel: +81 03 9411140 fax: +81 03 9413169 http://www.spring8.or.jp/top.html Tipo: D Status: C

SOLEIL Centre Universitaire - B.P. 34 - 91898 Orsay Cedex http://www.soleil.u-psud.fr/ Tipo: D Status:C

SOR-RING Inst. Solid State Physics S.R. Lab, Univ. of Tokyo, 3-2-1 Midori-cho Tanashi-shi, Tokyo 188, Japan tel: +81 424614131 ext 346 fax: +81 424615401 Tipo: D Status: O

SSRL Stanford SR Laboratory 2575 Sand Hill Road, Menlo Park, California, 94025, USA tel: +1 650-926-4000 fax: +1 650-926-3600 http://www-ssrl.slac.stanford.edu/welcome.html Tipo: D Status: O

SRS Daresbury SR Source SERC, Daresbury Lab, Warrington WA4 4AD, U.K. tel: +44 925 603000 fax: +44 925 603174 E-mail: srs-ulo@dl.ac.uk http://www.dl.ac.uk/home.html Tipo: D Status: O

SURF III B119, NIST, Gaithersburg, MD 20859, USA tel: +1 301 9753726 fax: +1 301 8697628 http://physics.nist.gov/MajResFac/surf/surf.html Tipo: D Status: O

TERAS ElectroTechnical Lab. 1-1-4 Umezono, Tsukuba Ibaraki 305, Japan tel: 81 298 54 5541 fax: 81 298 55 6608 Tipo: D Status: O

UVSOR Inst. for Molecular ScienceMyodaiji, Okazaki 444, Japan tel: +81 564 526101 fax: +81 564 547079 Tipo: D Status: O

SRC Synchrotron Rad. Center Univ.of Wisconsin at Madison, 3731 Schneider DriveStoughton, WI 53589-3097 USA tel: +1 608 8737722 fax: +1 608 8737192 http://www.src.wisc.edu Tipo: D Status: O

SRRC SR Research Center 1, R&D Road VI, Hsinchu Science, Industrial Parc, Hsinchu 30077 Taiwan, Republic of China tel: +886 35 780281 fax: +886 35 781881 http://www.srrc.gov.tw/ Tipo: D Status: O

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D = macchina dedicata

D = dedicated machine

PD = parzialmente dedicata

PD = partially dedicated

P = in parassitaggio

P = parassitic

O = macchina funzionante

O = operating machine

C = macchina in costruzione

C = machine under construction

FACILITIES

NEUTRONI NEUTRON SCATTERING WWW SERVERS IN THE WORLD (http://www.isis.rl.ac.uk) Atominstitut Vienna (A) Facility: TRIGA MARK II Type: Reactor. Thermal power 250 kW. Flux: 1.0 x 1013 n/cm2/s (Thermal); 1.7 x 1013 n/cm2/s (Fast) Address for information: 1020 Wien, Stadionallee 2 Prof. H. Rauch Tel: +43 1 58801 14111; Fax: +43 1 58801 14199 E-mail: boeck@ati.ac.at http://www.ati.ac.at Wap: wap.ati.ac.at

FRJ-2 Research Reactor in Jülich (D) Type: Dido reactor. Flux: 2 x 1014 n/cm2/s Prof. D. Richter, Forschungszentrums Jülich GmbH, Institut für Festkörperforschung, Postfach 19 13, 52425 Jülich, Germany Tel: +49 2461161 2499; Fax: +49 2461161 2610 E-mail: d.richter@kfa-juelich.de http://www.kfajuelich.de/iff/Institute/ins/Brosch uere_NSE/

IBR2 Fast Pulsed Reactor Dubna (RU) Type: Pulsed Reactor.

Flux: 3 x 1016 (thermal n in core) Address for application forms: Dr. Vadim Sikolenko, Frank Laboratory of Neutron Physics Joint Institute for Nuclear Research 141980 Dubna, Moscow Region, Russia.

Tel: +7 09621 65096; Fax: +7 09621 65882 E-mail: sikolen@nf.jinr.dubna.su http://nfdfn.jinr.ru/flnph/ibr2.html

NRU Chalk River Laboratories The peak thermal flux 3x1014 cm-2 sec-1 Neutron Program for Materials Research National Research Council Canada Building 459, Station 18 Chalk River Laboratories Chalk River, Ontario Canada K0J 1J0 Phone: 1 - (888) 243-2634 (toll free) Phone: 1 - (613) 584-8811 ext. 3973 Fax: 1- (613) 584-4040 http://neutron.nrccnrc.gc.ca/home.html

FRG-1 Geesthacht (D) Type: Swimming Pool Cold Neutron Source.

Flux: 8.7 x 1013 n/cm2/s Address for application forms and informations: Reinhard Kampmann, Institute for Materials Science, Div. WfnNeutronscattering, GKSS, Research Centre, 21502 Geesthacht, Germany Tel: +49 (0)4152 87 1316/2503; Fax: +49 (0)4152 87 1338 E-mail: reinhard.kampmann@gkss.de http://www.gkss.de

ILL Grenoble (F) Type: 58MW High Flux Reactor.

Flux: 1.5 x 1015 n/cm2/s Scientific Coordinator Dr. G. Cicognani, ILL, BP 156, 38042 Grenoble Cedex 9, France Tel: +33 4 7620 7179; Fax: +33 4 76483906 E-mail: cico@ill.fr and sco@ill.fr http://www.ill.fr

Budapest Neutron Centre BRR (H) Type: Reactor. Flux: 2.0 x 1014 n/cm2/s Address for application forms: Dr. Borbely Sándor, KFKI Building 10, 1525 Budapest, Pf 49, Hungary E-mail: Borbely@power.szfki.kfki.hu http://www.iki.kfki.hu/nuclear

HMI Berlin BER-II (D) Facility: BER II, BENSC Type: Swimming Pool Reactor. Flux: 2 x 1014 n/cm2/s Address for application forms: Dr. Rainer Michaelsen, BENSC, Scientific Secretary, Hahn-MeitnerInsitut, Glienicker Str 100, 14109 Berlin, Germany Tel: +49 30 8062 2304/3043; Fax: +49 30 8062 2523/2181 E-mail: michaelsen@hmi.de http://www.hmi.de/bensc

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IPNS Intense Pulsed Neutron at Argonne (USA) for proposal submission by e-mail send to cpeters@anl.gov or mail/FAX to: IPNS Scientific Secretary, Building 360 Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439-4814, USA Phone: 630/252-7820, FAX: 630/252-7722 http://www.pns.anl.gov/

IRI Interfaculty Reactor Institute in Delft (NL) Type: 2MW light water swimming pool.

Flux: 1.5 x 1013 n/cm2/s Address for application forms: Dr. A.A. van Well, Interfacultair

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FACILITIES

Reactor Institut, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands Tel: +31 15 2784738; Fax: +31 15 2786422 E-mail: vanWell@iri.tudelft.nl http://www.iri.tudelft.nl

LLB Orphée Saclay (F) Type: Reactor. Flux: 3.0 x 1014 n/cm2/s Laboratoire Léon Brillouin (CEACNRS) Submissio by email at the following address : experience@llb.saclay.cea.fr http://wwwllb.cea.fr/index_e.html

ISIS Didcot (UK) Type: Pulsed Spallation Source.

Flux: 2.5 x 1016 n fast/s Address for application forms: ISIS Users Liaison Office, Building R3, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX Tel: +44 (0) 1235 445592; Fax: +44 (0) 1235 445103 E-mail: uls@isis.rl.ac.uk http://www.isis.rl.ac.uk

NFL Studsvik (S) Type: 50 MW reactor. Flux: > 1014 n/cm2/s Address for application forms: Dr. A. Rennie, NFL Studsvik, S-611 82 Nyköping, Sweden Tel: +46 155 221000; Fax: +46 155 263070/263001 E-mail: user.admin@studsvik.uu.se http://www.studsvik.uu.se

JAERI (J) Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken 319-11, Japan.

Jun-ichi Suzuki (JAERI); Yuji Ito (ISSP, Univ. of Tokyo); Fax: +81 292 82 59227 telex: JAERIJ24596 http://www.ndc.tokai.jaeri.go.jp/

NIST Research Reactor, Washington, USA National Institute of Standards and Technology-Gaithersburg, Maryland 20899 USA Center Office: J. Michael Rowe, 6210, Director NIST Center for Neutron Research mike.rowe@nist.gov http://www.ncnr.nist.gov/

JEEP-II Kjeller (N) Type: D2O moderated 3.5% enriched UO2 fuel.

Flux: 2 x 1013 n/cm2/s Address for application forms: Institutt for Energiteknikk K.H. Bendiksen, Managing Director, Box 40, 2007 Kjeller, Norway Tel: +47 63 806000, 806275; Fax: +47 63 816356 E-mail: kjell.bendiksen@ife.no http://www.ife.no

NRI Rez (CZ) Type: 10 MW research reactor.

Address for informations: Zdenek Kriz, Scientif Secretary Nuclear Research Institute Rez plc, 250 68 Rez Czech Republic Tel: +420 2 20941177 / 66173428 Fax: +420 2 20941155 E-mail: krz@ujv.cz / brv@nri.cz http://www.nri.cz

NOTIZIARIO NEUTRONI E LUCE DI SINCROTRONE

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Vol. 9 n. 2 July 2004

PSI-SINQ Villigen (CH) Type: Steady spallation source.

Flux: 2.0 x 1014 n/cm2/s Contact address: Paul Scherrer Institut SINQ Scientific Coordination Office CH-5232 Villigen PSI Phone: +41 56 310 2087 Fax: +41 56 310 2939 E-mail: sinq@psi.ch http://sinq.web.psi.ch

SPALLATION NEUTRON SOURCE, ORNL (USA) http://www.sns.gov/

TU Munich FRM, FRM-2 (D) Type: Compact 20 MW reactor.

Flux: 8 x 1014 n/cm2/s Address for information: Prof. Winfried Petry, FRM-II Lichtenbergstrasse 1, 85747 Garching Tel: 089 289 14701 Fax: 089 289 14666 E-mail: wpetry@frm2.tum.de http://www.frm2.tu-muenchen.de