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NOTIZIARIO Neutroni e Luce di Sincrotrone

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SUMMARY EDITORIAL

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C. Andreani

SCIENTIFIC REVIEWS Fragility and bioprotective effectiveness by elastic neutron scattering ........................................................................ 3 S. Magazù, G. Maisano, F. Migliardo, C. Mondelli

NOTIZIARIO Neutroni e Luce di Sincrotrone published by CNR in collaboration with the Faculty of Sciences and the Physics Department of the University of Rome “Tor Vergata”. Vol. 10 n. 2 Luglio 2005 Autorizzazione del Tribunale di Roma n. 124/96 del 22-03-96 EDITOR:

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SCIENTIFIC REVIEWS Paper received March 2005

FRAGILITY AND BIOPROTECTIVE EFFECTIVENESS BY ELASTIC NEUTRON SCATTERING S. Magazùa*, G. Maisanoa, F. Migliardoa, C. Mondellib Dipartimento di Fisica and INFM, Università di Messina, P.O. Box 55, I-98166 Messina, Italy

Abstract Neutron intensity elastic scans on trehalose, maltose, sucrose/H2O mixtures as a function of concentration, temperature and exchanged wave vector are presented. The experimental findings show a cross-over in molecular fluctuations between harmonic and anharmonic dynamical regimes. The “stronger” character of trehalose/H2O mixture indicates a better attitude in respect to maltose and sucrose/H2O mixtures to encapsulate biostructures in a more rigid matrix.

mulated (Green and Angell, 1989; Crowe et al., 1998; Donnamaria et al., 1994), the effectiveness mechanisms remain still cryptic. Although many studies have been focussing on ternary systems such as biostructure/water/disaccharide (Cordone et al., 1998; Cordone et al., 1999; Cottone et al., 2001), some researchers retain that the protein dynamics as a whole is slave to the environment properties (Paciaroni et al., 2002; Frauenfelder et al., 1991; Frauenfelder and McMahon, 1998). In this frame Green and Angell (Green and Angell, 1989) suggest that the higher value of the glass transition temperature of trehalose and its mixtures with water, in comparison with the other disaccharides, is the only reason for its superior bioprotectant effectiveness. In fact the higher Tg values of the trehalose/H2O mixtures, in respect to those of the other disaccharides/H2O mixtures, implies that at a given temperature the glass transition for trehalose mixtures always occurs at a higher water content. As a matter of fact such a hypothesis alone is not entirely satisfactory if one keeps in mind that other similar systems, such as for example dextran ((C6H10O5)x) (Oliver et al., 1998), a linear polysaccharide with α(1-6) glycosidic links, present even a higher Tg value, but do not show comparable bioprotective action. Crowe and co-workers (Crowe et al., 1998) formulated the hypothesis that a direct interaction between the sugars and the object of protection occurs. More specifically their “water replacement hypothesis” justifies the trehalose protective function with the existence of direct hydrogen bonding of trehalose with the polar head groups of the lipids as water does. This hypothesis is supported by a simulation of Grigera and co-workers (Donnamaria et al., 1994), which argue that the structure of trehalose is perfectly adaptable to the tetrahedral coordination of pure water, whose structural and dynamical properties are not significantly affected by trehalose. As a matter of fact experimental findings obtained by several spectroscopic techniques (Branca et al., 2002a; Branca et al., 1999a; Magazù et al., 1997; Branca et al., 1999b; Magazù et al., 2001; Branca et al. 2001a; Branca et al., 2002b; Branca et al. 2001b, Magazù et al., 2004) indicate that the structural and the dynamical properties of water result drastically perturbed by disaccharides, and

Introduction In recent years a lot of attention has been addressed to the understanding of the mechanisms present in organisms able to survive under environmental stress conditions (Crowe et al., 1984). Cryptobiosis, from Greek κριπ− τοσ, “hidden” and “coated” and βιοσ, “life”, refers to a particular state of organisms inactivating when prohibitive environmental conditions occur. During cryptobiosis, undetectable (hidden) levels of metabolic functions are maintained, these levels reaching normal values when external conditions become again favourable to life (Crowe and Cooper, 1971; Hirsh, 1987; Storey and Storey, 1992). These extraordinary “cryptobiotic” organisms (the first one was documented by Anton van Leeuwenhoek in 1702) belong to all the natural kingdoms (Lee et al., 1992; Miller, 1978; Zentella et al., 1999). Cryptobiotic activating substances are certainly homologues disaccharides (C12H22O11, e. g. trehalose, maltose, sucrose with particular reference to trehalose, see Fig. 1), but in spite of the several bioprotection hypotheses for-

Figure 1. Structure of trehalose.

INFM-Operative Group Grenoble CRG IN13 and Institut Laue-Langevin, 38042 Grenoble Cedex 9, France

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in particular by trehalose. More specifically neutron diffraction results (Branca et al., 2002a) show for all disaccharides, and for trehalose to a large extent, a strong distortion of the peaks linked to the hydrogen bonded network in the partial radial distribution functions which can be attributed to the destroying of the tetrahedral coordination of pure water. Analogously Raman scattering findings (Branca et al., 1999a) show that the addition of trehalose, in respect to the other disaccharides, more rapidly destroys the tetrahedral intermolecular network of water, which by lowering temperature would give rise to ice. These results clearly indicate that disaccharides show a noticeable “kosmotrope” character, namely the disaccharide-water molecule interaction strength is much higher in respect to that between the water molecules. Furthermore ultrasonic velocity measurements (Magazù et al., 1997; Branca et al., 1999b) point out that, in respect to the other disaccharides, the trehalose-water system is characterized, in all the investigated concentration range, by both the highest value of the solute-solvent interaction strength and of hydration number. As far as dynamics is concerned Quasi Elastic Neutron Scattering (QENS) results on disaccharides solutions (Magazù et al., 2001) indicate that also the water dynamics is strongly affected by the presence of disaccharides and by trehalose in particular, contrarily to the predictions of Grigera’s simulation (Donnamaria et al., 1994). Furthermore viscosity measurements on trehalose, maltose, and sucrose aqueous solutions (Branca et al. 2001b) highlight that trehalose shows in respect to the other disaccharides, a “stronger” kinetic character in the Angell’s classification scheme. QENS and Inelastic Neutron Scattering (INS) were also employed to investigate the low frequency dynamics across the glass transition of trehalose, maltose and sucrose water mixtures (Branca et al. 2001a; Branca et al., 2002b). The obtained experimental findings, through the relaxational to the vibrational contribution ratio, confirm that the trehalose/H2O mixture shows a stronger character and furnish for it a higher force pseudo-constant (resilience) value in comparison to that of the other disaccharides/H2O mixtures. In this work elastic neutron intensity results on homologues disaccharides (trehalose, maltose, sucrose)/H2O mixtures as a function of concentration and temperature are presented. As we shall see the experimental findings allow to characterize the systems “flexibility” and fragility, which justify the better cryptoprotectant effectiveness of trehalose. Experimental The Instrument Elastic incoherent neutron scattering experiments were performed by using the IN13 spectrometer at the Insti-

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tute Laue Langevin (ILL) in Grenoble (France). The IN13 instrument is schematically shown in Fig. 2A e 2B. The relatively high energy of the incident neutrons (16 meV) makes it possible to span a wide range of momentum

Figure 2. (A) Scheme and (B) picture of the IN13 spectrometer.

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transfer Q (≤5.5 Å-1) with a very good energy resolution (FWHM) (~8 µeV). The monochromator and analyser CaF2(422) crystals (see Fig. 3) are oriented in near backscattering geometry

consisting of 32 He3 detector tubes, arranged in staggered circular rows, or with five individual He3 end window counters. The small Q range from 0.3 to 0.8 Å-1 is covered by a PSD detector. Neutrons with a 1 Å wavelength and an energy close to 1 kcal/mol represent excellent probe to characterize thermal molecular motions and conformational changes in biological systems (Zaccai, 2000; Doster et al., 1989; Smith, 1991; Bicout and Zaccai, 2001). In particular they furnish information on mean-square fluctuations in a given time scale by elastic scattering (Zaccai, 2000); on correlation times of diffusion motions by quasi elastic scattering (Doster et al., 1989); and on vibrational modes by inelastic scattering (Smith, 1991). The elastic experiments are the most efficient to perform, having the best signal-to-noise ratio (Smith, 1991; Bicout and Zaccai, 2001; Réat et al., 2000). The mean square displacements obtained by an analysis as a function of Q are dominated by hydrogen motions due to its large incoherent cross section value (Smith, 1991). In complex biological structures hydrogens move together with larger chemical groups and therefore their motion corresponds to the global thermal behaviour of the system (Bicout and Zaccai, 2001; Réat et al., 2000). The Experiment Ultra pure powdered trehalose, maltose and sucrose, and H2O, purchased by Aldrich-Chemie, were used for the experiments. Measurements were performed in a temperature range of 20÷310K on hydrogenated trehalose, maltose and sucrose in H2O and on partially deuterated trehalose, maltose and sucrose in D2O at weight fraction values corresponding to 19 and 6 water (H2O and D2O) molecules for each disaccharide molecule. In the used IN13 configuration for the measurements the incident wavelength was 2.23 Å and the Q-range was 0.28÷4.27 Å-1. Raw data were corrected for cell scattering and detector response and normalized to unity at Q=0Å-1.

Figure 3. Analysers of CaF2(422) crystals (in grey). One can distinguish the image of the 3 analysers on the PSD detector.

thereby achieving an energy resolution of few µeV. A vertically curved graphite deflector focuses the beam onto the sample. The scattered neutrons are energy analysed by a set of seven spherically curved composite crystal analysers, each covering a large solid angle of 0.18 sr. An additional three circular analysers centred around the transmitted beam cover the small-angle region. A chopper is used to suppress (i) the background of neutrons scattered directly from the sample into the detectors and (ii) second order contamination. The neutrons are counted either with a cylindrical multidetector

Results and Discussion In Fig. 4 a comparison among elastic incoherent neutron scattering spectra of trehalose+19H 2 O and sucrose+19H2O mixtures is shown. It is evident that a dynamical transition occurs for the trehalose/H2O mixture at T~238K and sucrose/H2O mixtures at T~233K. In the insert the elastic intensity versus temperature of trehalose+6H2O, sucrose+6H2O, trehalose+19D2O and sucrose+19D2O mixtures are reported. For all the samples below the onset temperature the elastic intensity has the Gaussian form expected for a harmonic solid (Doster et al., 1989; Smith, 1991; Bicout and Zaccai, 2001). The decrease in the elastic intensity above the dynamical transition temperature can be attributed to the excitation of new degrees of freedom (Doster et al., 1989), especially

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at low Q, and is very less marked in the case of trehalose/water mixture than for the other disaccharide/ water mixtures. This circumstance clearly indicates that trehalose shows a larger structural resistance to temperature changes and a higher “rigidity” in comparison with the sucrose/H2O mixture, this latter showing a “softer” character. With the purpose of connecting the bioprotectant effectiveness of disaccharide/H2O mixtures to the “fragility degree” of these systems, we introduce a new operative definition for fragility, based on the evaluation by neutron scattering of the temperature dependence of the mean square displacement. The procedure is based on the relation between a macroscopic transport quantity,

Figure 4. Elastic incoherent neutron scattering spectra S(Q,ω=0) of trehalose+19H2O mixture (black circles) and sucrose+19H2O mixture (red squares) as a function of temperature. In the insert the elastic intensity vs temperature of trehalose+6H2O mixture (blue circles), sucrose+6H2O mixture (orange squares), trehalose+19D2O mixture (magenta circles) and sucrose+19D2O mixture (violet squares) are reported.

viscosity, and an atomic quantity, the nanoscopic mean square displacement. As it is well known, the behavioural properties of a glass-forming system can be described in terms of the (3N+1)-dimensional potential energy hyper-surface in the configurational space (Angell et al., 1994; Angell, 1997). The complexity of the energy landscape, explored by the system, can be correlated with the density of the minima of the hyper-surface (degeneracy ∝∆Cp(Tg)) and with the distribution of the barrier heights between them ∆µ. These topological features of potential energy hyper-surface determine the structural sensitivity of a system to temperature changes in approaching the glass transition, namely its “fragility” (∝∆Cp(Tg)/∆µ) , which is operatively defined as:

d log η d (Tg T )

(1) T = Tg+

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In the Angell’s classification of glass-forming systems (Angell et al., 1994; Angell, 1997), based on the choice of an invariant viscosity at the scaling temperature T g (η(Tg)=1013 poise), the departure from the Arrhenius law is taken as a signature of the degree of fragility of the system (Angell et al., 1994; Angell, 1997). An Arrhenius behaviour of viscosity in the Tg-scaled plot and a small heat capacity variation ∆Cp(Tg) characterize the strongest systems, whereas a large departure from Arrhenius law and a large heat capacity variation ∆Cp(Tg) characterize the most fragile ones. Between these two limiting cases, intermediate behaviours can be interpreted in terms of different kinetic (η) and thermodynamic contributions (∆Cp(Tg)): thermodynamically strong (small ∆Cp(Tg)) and kinetically fragile systems (non-Arrhenius η behaviour) are characterized by a low minima density of the potential energy hyper-surface and low energy barriers. Vice versa thermodynamically fragile (large ∆Cp(Tg)) and kinetically strong systems (Arrhenius η behaviour) are characterized by a high hyper-surface configurational degeneracy and high barrier heights. On the other hand Sokolov et al. (Sokolov et al. 1993; Sokolov et al., 1994), taking into account low-frequency Raman data, in order to characterize the fragility degree of glass-forming systems introduced the ratio of the normalized Raman intensity In=I/{ω[n(ω)+1]} at the minimum, (I n) min, to the intensity of the so called “boson peak” maximum, (In)max, R1= (Imin)/(Imax). Through the evaluation of the R1(T) parameter at the glass transition, these authors have found a close correlation between the ratio of the relaxational to the vibrational contribution and the degree of fragility (Sokolov et al., 1994). Defining <u 2> loc as the difference between the mean square displacements of the disordered phases (amorphous and liquid) and the ordered phase (crystalline):

<u2>loc=<u2>disord-<u2>ord

(2)

a linear relation is observed between the logarithm of viscosity and the inverse of <u2>loc. This linear relation includes both the region below the glass transition temperature and above the melting temperature. On the basis of the linear dependence of log η versus (<u2>loc)–1 the following interpretative model for the elementary flow process (α-relaxation) can be proposed. A given particle is jumping back and forth in the fast processes (β-relaxation) with a Gaussian probability distribution of mean square amplitude <u2>loc. When the amplitude of that fast motion exceeds a critical displacement u0, a local structural reconfiguration (α-relaxation) takes place. Under the assumption of temperature independence of the time scale of the fast motion, the waiting time for the occurrence of a α process at a given particle is proportional to the probability to find the particle out-

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side the sphere with radius u0. Within this picture, one can express viscosity with the following expression:

[

η = η0 exp u02 u 2

loc

]

(3)

Taking into account Eqs. 1-3, a new operative definition for characterizing the “fragility” degree by elastic neutron scattering can be introduced (Magazù et al., 2004):

(

d u02 u 2

loc

d (Tg T )

)

(4) T = Tg+

Obviously such a definition implies a fragility parameter depending on the instrumental resolution, which determines the observation time scale. However we are inter€ ested on a comparison ceteris paribus of the fragility degree and such a comparison is meaningful for the same resolution value. In fact coherent results are obtained also for other glass-forming systems, such as B2O3 (Engberg et al., 1998), glycerol (Wuttke et al., 1995), PB (Frick and Richter, 1995), o-terphenyl (Tölle et al., 2000) and selenium (Buchenau and Zorn, 1992). From Eq. 4 we evaluate a fragility parameter M of 302 for the trehalose+19H2O mixture and of 355 for the sucrose+19H2O mixture. Employing a less wide viscosity data sets, for trehalose/D2O and sucrose/D2O mixtures at a concentration value corresponding to 19 water molecules for each disaccharide molecule we obtain a fragility parameter M of 272 and of 295, respectively, whereas for the trehalose/H2O and sucrose/H2O mixtures at a concentration value corresponding to 6 water molecules for each disaccharide molecule we obtain for the fragility parameter M the value of 241 and of 244, respectively. Table I reports some of the values of fragility parameters Compound

Tg (K)

m, R1 and M as obtained by viscosity measurements (m) (Sokolov et al., 1994; Branca et al., 2001b), Raman (Sokolov et al., 1994) and neutron scattering by the analysis of the relaxational and vibrational contribution (R1) (Sokolov et al., 1994), by elastic neutron scattering (M) by IN13 working with a resolution of 8 µeV (Wuttke et al., 1995; Frick and Richter, 1995; Tölle et al., 2000) and by IN6 (B2O3 and selenium) working with a resolution of 150-200 µeV (Buchenau and Zorn, 1992; Engberg et al., 1998). The reported values indicate that the present operative definition for fragility furnishes an excellent direct proportionality between M and m. In fact if one reports on a plot the R1 parameter, as defined by Sokolov (Sokolov et al. 1993; Sokolov et al., 1994), versus m (see Fig. 5A), one realises

R1(Tg) R1(Tg) neutron Raman

SiO2

1446

0.50

B2O3

526

Glycerol

186

0.60

0.41

181

188

0.95

Trehalose + 19 H2O

238

302

0.61

Sucrose + 19 H2O

233

355

0.73

o-terphenyl

243

483

1.0

Selenium

305

120

0.39

0.70

Table I. Values of fragility as obtained viscosity measurements (Sokolov et al., 1994; Branca et al., 2001b), Raman (Sokolov et al., 1994) and neutron scattering by analysis of the relaxational and vibrational contribution (Sokolov et al., 1994), by elastic neutron scattering by IN13 working with a resolution of 8 µeV (Wuttke et al., 1995; Frick and Richter, 1995; Tölle et al., 2000) and by IN6 working with a resolution of 150-200 µeV (Buchenau and Zorn, 1992; Engberg et al., 1998).

Figure 5. (A) R1(Tg) parameter, as defined by Sokolov (Sokolov et al. 1993; Sokolov et al., 1994), versus the fragility parameter m. The solid black line is a guide for eyes. (B) Linear behaviour of the M fragility parameter, as defined in the present work, versus the fragility parameter m. The variously coloured points are experimental data obtained by using the IN13 spectrometer at a instrumental elastic energy resolution of 8 µeV (FWHM) (Wuttke et al., 1995; Frick and Richter, 1995; Tölle et al., 2000); the black points are experimental data obtained by using the IN6 spectrometer at a instrumental elastic energy resolution of 150-200 µeV (FWHM) (Buchenau and Zorn, 1992; Engberg et al., 1998). The solid blue line indicates the best fit.

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that the experimental points are quite spread out along a linear behaviour and that, therefore, the quantitative evaluation of the fragility factor R1 suffers of a certain indeterminacy. On the other hand when the M parameters, obtained with a given resolution, are reported as a function of m, see Fig. 5B, the data arrange themselves on a straight line whose slope depends uniquely on the instrumental resolution. From this analysis it clearly emerges that the trehalose/H2O mixture is characterized in respect to the maltose/H 2O and sucrose/H 2O mixtures by a lower fragility namely by a higher resistance to local structural changes when temperature decreases towards the glass transition value. In order to unravel the physical mechanisms which determine such peculiar trehalose’s behaviour we have performed INS experiments on trehalose/H 2O, maltose/H 2O and sucrose/H 2O mixtures by the TOSCA spectrometer at the ISIS facility (Chilton, UK). An important feature in the bending modes vibrational spectral region, see Fig. 6, is that the intensity profile of trehalose in this INS region appears more “structured”, i.

entity, which shows a more crystalline character, which makes it able to protect biological structures in a more rigid environment. Such a property can be summarized saying that trehalose maintains a more “cryptocrystalline” behaviour namely a locally more “ordered” structure, which justifies its lower fragility. This cryptocrystalline conformation could be linked to a glacial phase (Ha et al., 1996; Hédoux et al., 1998; Hédoux et al., 2002), an apparently amorphous phase in which nanocrystallized domains of the stable crystalline phase are mixed with remaining liquid. In our opinion this circumstance is relevant because it implies a better cryptobiotic effect and hence a higher capability of cryptoprotection at high disaccharide concentration. Conclusions It is curious that some of the cryptic secrets of trehalose lie just in the etymologic definition of its most appropriate adjective: κριπτοσ, which contains the reference to the “hidden” life of cryptobiosis and to “cover” i. e. the capability to encapsulate the biostructures to protect, creating a protecting shell characterized by “cryptocrystallinity”, i.e. the capability to give rise to a (hidden) nanoscopic crystalline structure which is responsible for the higher structural resistance. Acknowledgements The authors gratefully acknowledge the Institut LaueLangevin ILL (Grenoble, France) and Marc Bee for dedicated runs at IN13 spectrometer, and the ISIS facility (Chilton, UK) and Anibal Ramirez-Cuesta for dedicated runs at TOSCA spectrometer. We acknowledge the financial support of the Consiglio Nazionale delle Ricerche (CNR)-Italy within the CNRCCLRC agreement.

Figure 6. Comparison among trehalose/H2O mixture (black line), maltose/H2O mixture (blue line) and sucrose/H2O mixture (red line) in the INS bending (1060÷2000 cm-1) spectral region. The disaccharides mixtures profiles are shifted for clarity.

e. trehalose shows in comparison with the other disaccharides the most “crystalline” character. In more detail, trehalose shows more distinctly, in respect to the other disaccharides, the characteristic three peaks typical of the crystalline state at ~1118 cm-1, ~1240 cm-1 and ~1365 cm-1, which can be linked to the hybridized H-C-H, C-CH and C-O-H bending modes of the trehalose molecule as suggested by a density functional simulation of Magazù et al. (Ballone et al., 2000). Such a result clearly indicates that trehalose, besides modifying significantly the structural and dynamical properties of water, forms with H2O molecules a unique

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References 1. Angell, C. A., P. H. Poole, J. Shao. 1994. Il Nuovo Cimento D 16:9931025. 2. Angell, C. A. 1997. Prog. Theoret. Phys. 126:1-7. 3. Ballone, P., N. Marchi, C. Branca, S. Magazù. 2000. J. Phys. Chem. 104:6313-6317. 4. Bicout, D. J., G. Zaccai. 2001. Biophys. J. 80:1115-1123. 5. Branca, C., S. Magazù, F. Migliardo. 2002a. Rec. Res. Develop. in Phys. Chem. 6:35-73. 6. Branca, C., S. Magazù, G. Maisano, P. Migliardo. 1999a. J. Chem. Phys. 111:281-287. 7. Branca, C., A. Faraone, S. Magazù, G. Maisano, F. Migliardo, P. Migliardo, V. Villari. 1999b. Rec. Res. Develop. in Phys. Chem. 3:361-403. 8. Branca, C., S. Magazù, G. Maisano, F. Migliardo. 2001a. Phys. Rev. B 64:2242041-2242048. 9. Branca, C., S. Magazù, G. Maisano, F. Migliardo, G. Romeo. 2002b. Philos. Mag. B 82:347-355. 10. Branca, C., S. Magazù, G. Maisano, F. Migliardo, G. Romeo. 2001b. J. Phys. Chem. B 105:10140-10145. 11. Buchenau, U., R. Zorn. 1992. Europhys. Lett. 18:523-528.

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12. Burattini, E., M. Federico, G. Galli, S. Magazù, D. Majolino.1988. Il Nuovo Cimento D 10:425-434. 13. Cordone, L., P. Galajda, E. Vitrano, A. Gassman, A. Ostermann, F. Parak. 1998. Biophys. J. 27:173-176. 14. Cordone, L., M. Ferrand, E. Vitrano, and G. Zaccai. 1999. Biophys. J. 76:1043-1047. 15. Cottone, G., L. Cordone, G. Ciccotti. 2001. Biophys. J. 80:931-938. 16. Crowe, J. H., and L. M. Crowe. 1984. Science. 223:701-703. 17. Crowe, J. H., and A. F. Jr. Cooper. 1971. Scientific American 225:30-36. 18. Crowe, J. H., J. S. Clegg, L. M. Crowe. 1998. In The Roles of Water in Foods. D. S. Reid, editor. Chapman & Hall, New York. 440-455. 19. Donnamaria, M. C., E. I. Howard, and J. R. Grigera. 1994. J. Chem. Soc. Faraday Trans. 90:2731-2735. 20. Doster, W., S. Cusack, and W. Petry. 1989. Nature. 337:754-756. 21. Engberg, D., A. Wischnewski, U. Buchenau, L. Börjesson, A. J. Dianoux, A. P. Sokolov, and L. M. Torell. 1998. Phys. Rev. B 58:9087-9097. 22. Frauenfelder, H., S. G. Sligar, and P. G. Wolynes. 1991. Science. 254:1598-1603. 23. Frauenfelder, H., and B. McMahon. 1998. Proc. Natl. Acad. Sci. U.S.A. 9995:4795-4797. 24. Frick, B., D. Richter. 1995. Science 267:1939-1945. 25. Galli, G., P. Migliardo, R. Bellissent, W. Reichardt. 1986. Solid State Commun. 57:195-198. 26. Green, J. L., and C. A. Angell, 1989. J. Phys. Chem. B. 93:2880-2882. 27. Ha, A., I. Cohen, X. Zhao, M. Lee, D. Kivelson. 1996. J. Phys. Chem. 100:1-4. 28. Hédoux, A., Y. Guinet, M. Descamps. 1998. Phys. Rev. B 58:31-34. 29. Hédoux, A., Y. Guinet, M. Foulon, M. Descamps. 2002. J. Chem. Phys. 116:9374-9382.

30. Hirsh, A. 1987. Cryobiology. 24:214-228. 31. Lee, R. E. Jr., J. P. Costanzo, E. C. Davidson, and J. R. Jr. Layne. 1992. J. Therm. Biol. 17:263-266. 32. Magazù, S., P. Migliardo, A. M. Musolino, M. T. Sciortino. 1997. J. Phys. Chem. 101:2348-2351. 33. Magazù, S., V. Villari, P. Migliardo, G. Maisano, M. T. F. Telling. 2001. J. Phys. Chem. 105:1851-1855. 34. Magazù, S., G. Maisano, F. Migliardo, C. Mondelli. 2004. Biophys. J. 86:3241-3249. 35. Miller, L.K. 1978. Comp. Biochem. Physiol. 59A:327-334. 36. Oliver A. E., L. M. Crowe, J. H. Crowe. 1998. Seed Sci. Res. 8:211–221. 37. Paciaroni, A., S. Cinelli, G. Onori. 2002. Biophys. J. 83:1157-1164. 38. Réat, V., R. Dunn, M. Ferrand, J. L. Finney, R. M. Daniel, and J. C. Smith. 2000. Proc. Natl. Acad. Sci. USA. 97:9961-9966. 39. Smith, J. C. 1991. Q. Rev. Biophys. 24:227-291. 40. Sokolov, A. P., A. Kisliuk, D. Quitmann, E. Duval. 1993. Phys. Rev. B 48:7692-7698. 41. Sokolov, A. P., A. Kisliuk, D. Quitmann, A. Kudlik, E. Rössler. 1994. J. Non-Cryst. Sol. 172-174:138-153. 42. Storey, K. B., and J. M. Storey. 1992. Annu. Rev. Physiol. 54:619-637. 43. Tölle, A. H. Zimmermann, F. Fujara, W. Petry, W. Schmidt, H. Schober, and J. Wuttke. 2000. Eur. Phys. J. B 16:73-80. 44. Wuttke, J., W. Petry, G. Coddens, F. Fujara. 1995. Phys. Rev. E 52:40264034. 45. Zaccai, G. 2000. Science. 288:1604-1607. 46. Zentella, R., J. O. Mascorro-Gallardo, P. Van Dijck, J. Folch-Mallol, B. Bonini, C. Van Vaeck, R. Gaxiola, A. A. Covarrubias, J. Nieto-Sotelo, J. M. Thevelein, and G. Iturriaga. 1999. Plant Physiol. 119:1473-1482.

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Paper received April 2005

FOCUS ON THE CHEMICAL AND ELECTRONIC STRUCTURE OF BIOMIMETIC PORPHYRINS HIGHLIGHTED WITH SR EXPERIMENTS AND THEORY Giovanni Polzonetti Dipartimento di Fisica e INFM, INSTM, CISDiC, Università “Roma Tre”, Via della Vasca Navale 84, 00146 Roma, Italy

Abstract Synchrotron Radiation Spectroscopy studies, XPS and NEXAFS, were a foremost way to investigate the multifaceted properties of porphyrin based complexes with increasing molecular complexity. The assignment of the resonances and the statements related to chemical shifts were accomplished with the aid of theory applied to the synthesized as well as to model molecules. The supramolecular behavior of porphyrin/fullerene hybrids, promising materials in the applications for nano-devices, was also revealed by combining the two spectroscopies. Introduction In the framework of porphyrin molecules, a strong effort has been given along the years in the synthesis of peculiar structures containing porphyrin based molecules. The chemistry that can be played within this family of molecules is huge and almost without frontier. The tailoring of discrete ordered arrays of porphyrins and metalloporphyrins has recently produced a synthetic methodology with a building block approach. Therefore, by the time and during the last 10 years a significant development in the realization of oligoporphyrins and oligometalloporphyrins has given rise to a large variety of new and interesting compounds with potential use for the realization of devices for chemical sensors in electron and energy transfer. In order to give to the readers an idea of the importance of this class of molecules, in the framework of animal and vegetal life, it is worth to mention that both hemoglobin and chlorophyll are porphyrin molecules. The word porphyrin is consequent from the Greek porphura meaning purple, and all porphyrins come into view strongly colored in the visible light. Typically, multiporphyrin systems have been considered as biomimetic models or resources for moving energy, charge, molecules and ions and as catalysts. Arrays are useful on every instance a specific molecular arrangement in space is crucial for an efficient process. Therefore, these macromolecular assemblies are also widely employed as models for studies on energy transfer, to shed light on light-harvesting processes in photosynthetic systems [1]. Their chemical-physical properties depend primarily on

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the nature of the linkage between porphyrin building blocks. It is well-known that the electronic structure and molecular geometry of these systems strongly influences the transfer of electronic charge, and, typically, the distance between bridged porphyrin-porphyrin macrocycles plays a foremost role in allowing high excitonic and electronic coupling between chromophore centers. The organic or organometallic spacers, used as bridging groups between porphyrin moieties are significant for both molecular and electronic properties of multiporphyrin arrays. Among the others, because of their peculiar properties such as for instance the building of extended π-systems, porphyrins are also good candidates for applications in the field of NLO (Non Linear Optical) materials [3, 4], for electronic devices in telecommunications, information storage and optical switches [5], molecular wires [6], photon tunnels [7]. Conjugated porphyrin polymers are giant supramolecular chromophores with extraordinary electrooptical and nonlinear optical properties and alkyne-linked oligomers have been most intensively investigated [8]. Keeping in mind the link between nature and research, many efforts have been directed to mimic the nature as for instance the structure and/or function of photosynthetic reaction center, including the primary events of the photosynthetic process that results in charge separation and subsequent electron transfer [9]. Synthetic routes have also been developed to achieve multiporphyrin arrays that can be the key for conversion and storage of the solar energy [10]. Fairly interesting appears also that such investigations may ultimately show the way to use the light energy adsorbed by oligoporphyrins and oligometalloporphyrins to drive endothermic chemical reactions, such as the conversion of water into H2 and O2, functional as a fuel supply [11]. Several examples of biochemical reactions deal with enzymatic systems (including hemoproteins) bringing more than one metal ion in the active center and in this context, a number of aspects of the sympathetic binding of dioxygen by hemoglobin, which carries four hemes, have been investigated by means of oligomeric metalloporphyrins [12]. Oligomeric metalloporphyrins have also been applied with accomplishment to explore

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various aspects of the process involving cytochrome c oxydase [13]. A newly recognized supramolecular feature is the attraction of the curved π surface of a fullerene to the center of the flat surface of a porphyrin or metalloporphyrin. The close association of a fullerene and a porphyrin has been highlighted in the molecular packing of a crystal structure containing a covalent system [14]. The fullereneporphyrin connection is thought to involve a π-π attraction as well as the interaction between the electron density of a 6:6 ring juncture of the fullerene (i.e. double bond) and the electropositive center of the porphyrin; the degree of charge transfer and its direction have become a subject of dispute. About these mixed systems there are promising applications in the areas of porous scaffold solids, NLO and photovoltaic devices. In the framework of this area of research we have investigated porphyrin and multiporphyrin samples as synthesized and upon interface formation with C60, and the present paper aims at giving a wide-ranging view of the investigated aspects. Experimental 1. Spectroscopy Synchrotron induced XPS and NEXAFS experiments were performed at LURE Super ACO (SACEMOR experimental station was used on the SA72 and SA22 beamlines connected to the bending magnet front end; the lines use a high-energy TGM and PGM respectively) and at ELETTRA storage ring using the SuperESCA beamline and relative experimental station built on three levels. The beamline is connected to an undulator front-end and has a SX700 monochromator, a custom designed electron analyzer and a multichannel plate detector with an istrumental resolution of ∆E/E= 10-4. The NEXAFS spectra were taken by measuring the total electron yield (I) emitted by the sample using a channeltron, while the reference absorption intensity (I0) was taken on the last focusing mirror by measuring the drain current. I and I0 were measured at the same time, thus avoiding any influence in the normalization process due to instability of the SR beam. In the multilayer conditions the absorption signal is given by the Isample/I0, whereas in the submonolayer and monolayer systems, the spectrum of the clean Cu(111) surface (Iclean/I0) was recorded before dosing and removed from the spectrum of the ZnPf2/Cu(111) sample (Isample/I0 ), by operating the ratio (Isample/I0) / (Iclean/I0); ZnPf2 is the porphyrin precursor used for our studies (see Fig. 2). The photon energy scale had been previously calibrated with gas phase nitrogen at the K-edge absorption. Spectra have been recorded in the photon energy range 395430 eV. All the spectra were normalized by fitting the part below the edge by a straight line taken as zero, and

assessing to 1 the electron yield at 425 eV. The photon polarization factor of the storage ring corresponds to 0.95. Photoelectron spectroscopy was performed in the fixed analyser transmission mode with the pass energy set to 20 eV. Photons of 497 and 87.5 eV energy have been used for the wide scan and N1s, C1s, VB and the Cu3p spectral regions respectively, with the monochromator entrance and exit slits fixed at 20 µm. Calibration of the energy scale was made by referencing all the spectra to the copper Fermi edge and the Zn3d signal was always found at about 10.5 eV. 2. Materials and synthesis Porphin (Pf) and C60 were commercial products (Sigma) used as received. 2,8,12,18-tetraethyl-5,15-diethynyl3,7,13,17-tetramethylporphyrin (PfNH) and 2,8,12,18tetraethyl-5,15-diethynyl-3,7,13,17-tetramethylporphyrinatozinc(II) (ZnPf2) were synthesized and purified in our laboratory [15]. The assembled samples, porphyrinbridged bis(tributylphosphine)platinum dimer dichloride Pt-ZnPf1 [1] and diporphyrin-bridged bis(triphenylphosphine)platinum dimer dichloride Pt-ZnPf2, diporphyrin-bridged bis(tributylphosphine)platinum dimer dichloride (Pt-ZnPf3) [16], were separated from the crude reaction products obtained following the procedures already reported. Thin film samples in the monolayer and multilayer regimes were obtained by a step-by-step sublimation of ZnPf2 onto a Cu(111) clean surface; completion of the monolayer coverage was estimated by XPS analysis of both substrate and adsorbate signals and particularly by the Fermi edge attenuation from the copper substrate. C60 overlayer growth was accomplished by sublimation as well. Mass spectrometry was used to check the purity of both ZnPf2 and C60 vapors before exposing to the Cu(111) surface. The Cu(111) crystal was cleaned by several cycles of sputtering and annealing to ~ 400°C and the cleanliness was checked by LEED. Results 1. Electronic structure and charge transfer effects in porphyrins Our approach for the study of porphyrin and multiporphyrin arrays follows a simple route which considers the simplest molecules of this family and then proceeds with the chemical substitution around the macro ring followed by the subsequent chemical modifications. This pathway was chosen in order to give an interpretation of the effects originating from the chemical changes performed on the molecule, i.e.: the external groups substitution, the metal insertion at the centre and the building of molecular arrays. On this base, we have started considering the simple porphin molecule Pf, i.e. a free porphyrin containing only hydrogen bonded to the car-

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bon atoms of the four pyrrolic rings, and the computed model Zn-porphin, ZnPf1, which structure is displayed in Fig. 1.

and in a drastic reduction of the energy separation between the π* levels, interpreted as due to an electron charge density enhancement at the nitrogen atoms.

Figure 1. Molecular structure of the model molecule Zn porphin (ZnPf1), i.e. the Zn(II) coordination compound of the simplest porphyrin molecule: porphin. Only hydrogens are bonded to the four penta atomic rings. Bond distances are also displayed.

Then the complexity of the molecule was enhanced introducing in turn 8 electron repulsive alkyl and 2 electron attractive ethynyl groups thus leading to PfNH. The reaction with Zn (II) gave the complex ZnPf2 with the metal in the core and next, the linkage between -PtCl(PR 3) 2 tethers (R=n-butyl, phenyl) and porphyrin bridging molecules led to arrays Pt-ZnPf1, Pt-ZnPf2, PtZnPf3, that showed an increased orbital delocalization. In Fig. 2 the chemical structures of these porphyrins (Pf, PfNH, ZnPf2) and one selected multiporphyrin arrays (Pt-ZnPf3) are displayed in order to give a clear pattern of the subsequent chemical modifications. XPS analysis evidenced the chemical inequivalence of the nitrogen atoms of Pf and PfNH, two by two, due to the difference in hybridization (sp2 and sp3 for =N- and N-H nitrogens respectively) producing differences in charge density reflected on the ionization potential at the N1s core level as high as 1.8 eV. The changes observed upon chemical groups substitution around the molecule evidenced that since the electron repulsive groups are the majority (8 against 2), the final effect is a significant increase of charge density at the nitrogen site; demonstrating the effectiveness of the charge delocalization. This effect has been clearly displayed either by XPS at the N1s core level and by the NEXAFS spectroscopy [16, 17] by a N1s core level shift of 0.5 eV and respectively by a π* resonances shift, 1÷2 eV, to a lower photon energy

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Figure 2. Molecular structures of porphin (Pf), 2,8,12,18-tetraethyl-5,15diethynyl-3,7,13,17-tetramethylporphyrin (PfNH), 2,8,12,18-tetraethyl5,15-diethynyl-3,7,13,17-tetramethylporphyrinatozinc(II) (ZnPf2), and the assembly with Pt tethers: diporphyrin-bridged bis(tributylphosphine)platinum dimer dichloride (Pt-ZnPf3). Me=methyl, Et=ethyl, Bu=butyl.

The situation changed again as soon as the porphyrin (PfNH) underwent the reaction with zinc ions. Complexation gave rise to a chromophore (ZnPf2) with the four nitrogen atoms that, even if still preserving their hybridization, should result nearly equivalent; the evidence for this has been quite marked with the occurrence of one single N1s core level signal in the XPS spectrum and a complete disappearance of the π* resonances assigned to the transitions associated to the protonated nitrogens. This last result did come out in the same way, either from the experiments as well as the calculations. Due to the complexity of the system, the NEXAFS analysis of this molecule at the N K-edge has been performed both experimentally and theoretically. To this purpose a relatively new computational approach based to the STEX method (Static Exchange) has been used

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[18]. The achieved results predicted two N1s→π* transitions into two excited states for each of the couples of nitrogens for the simple porphin and in addition a

Figure 3a. The N K-edge NEXAFS experimental spectrum for solid 2,8,12,18-tetraethyl-5,15-diethynyl-3,7,13,17-tetramethylporphyrin (PfNH). Dots stand for the experimental spectrum while solid lines are the result of fitting analysis using gaussian curves, dashed line is the background. The chemical structure of PfNH is also displayed.

Figure 3b. The experimental NEXAFS spectrum at the N K-edge of 2,8,12,18-tetraethyl-5,15-diethynyl-3,7,13,17-tetramethylporphyrinatozinc(II) (ZnPf2) solid film. Dots are for the experimental trace while solid lines result from the fitting by using gaussian functions, dashed line is the background. The chemical structure of ZnPf2 is also displayed.

broad band in the continuum assignable to excitation to an empty σ* orbital. As an example, the N K-edge NEXAFS experimental spectra of the porphyrin, PfNH, and of the Zn-porphyrin, ZnPf2 samples are reported in Fig. 3a and Fig. 3b respectively. The analysis of the experimental spectrum of Pf and PfNH (chemical structures reported in Fig. 2) is complicated by the low energy resolution in part of the π* resonance region and also by the intrinsic weakness of the π* features. Low intensity π* bands in NEXAFS spectra

were also observed in the porphyrins studied by other authors for the case of unoriented films [19]. In our opinion the low intensity of the π* resonances can also be due to a high delocalization of the excited electrons on the porphyrin ring. This is likely supported by our calculations at the N K-edge and also by the similarity with the spectra of randomly oriented ZnTPP and H2TPP (TPP = tetraphenylporphyrin) [19]. Several features (noted A to F in Fig. 3a) are clear in the spectrum. Owing to the previously discussed differences among the two couples of nitrogens, some of these resonances (A, C) belong to excitations at the (=N-) and some (B, D) at the (-NH-) nitrogens, as predicted by the theoretical simulation. Noticeable is the disappearance of the features associated to the (-NH-) nitrogens in Fig. 3b. The theoretical approach has been quite useful for the assignment of the resonances recorded in the experimental spectra and for the assessment of chemical-physical features related to the step-by-step modification of the molecular structure. The main results of this study are hereafter briefly underlined. In Fig. 4 the computed N K-edge NEXAFS spectra by the STEX method are reported for porphin and model Znporphyn (ZnPf1). For porphin the spectrum summation for the two not equivalent couples of nitrogens is displayed. The porphin spectrum shows four strongly prominent structures in the low energy region and two main features in the continuum. For every type of nitrogen in the molecule, two core electron excitations are placed into two energetically dissimilar π* orbitals, separated by 4.6 eV for (=N-) and 4.3 eV for (-NH-) respectively. The not protonated nitrogens =N- are accounted by the first and third π* resonances, while the result for the hydrogenated nitrogens -NH- give the second and fourth π* features. As expected by the considerations made about the chemical changes, the spectrum computed for Zn-porphin does not display any longer the couple of resonances by the two (-NH-) nitrogens. The splitting of the π* resonances is frequently described, in the “building block” model, as due to first order bond-bond interaction between two energetically degenerate orbitals [20]. This kind of splitting is automatically included in the ab-initio calculations and originates two π* orbitals characterized by contributions of the atomic p functions on the two nitrogen atoms with reversed sign (lowest energy peak) and the same sign (highest energy peak) correspondingly. The energy separation between the corresponding π* bands in =N- and NH- spectra, is 2.4 eV and 2.1 eV respectively. This energy diversity typically accounts for the ionization potential (IP) chemical shift due to the N-H bond and is fairly close to the ∆IP values originate by XPS: for instance 1.8 eV for PfNH [16] and 2.1 eV for octaethylporphyrin [21]. Concerning with the higher energy continuum region,

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as due to a lacking description of the σ* N-C excitation and to multi-electron excitations.

Figure 4. The NEXAFS spectra calculated for the Zn-porphin (ZnPf1) model molecule and Porphin (Pf) by the STEX method at the N K-edge. The lower panel displays the summation between the contributions by the two inequivalent =N- and –NH- couples of nitrogen atoms. The upper panel concerns the ZnPF1 complex and exhibits only the two contributions to the π* resonances originating by the four chemically equivalent nitrogens (=N-).

the similarities between –N= and –NH- resonances are remarkable. A broad shape resonance due to σ* N-C excitations occurs at 412 eV, followed by a much less pronounced one, also of σ symmetry, around 420 eV. A further spotlight of the importance of the theory in photoelectron spectroscopy studies concerning porphyrins is given by the comparison between theory and experiment that allowed for an unambiguous band assignment of the broad and intense band E above 406 eV in the experimental spectrum (Fig. 3a and Fig. 3b). This resonance does not have counterpart in the computed N K-spectrum, with no strong contribution to the cross section around 406-407 eV (Fig. 4). Shape resonances in the continuum are generally well described by the independent particle approximation. However, for shape resonances very close to the ionization threshold (as for feature E) we expect that electron correlation may be quite important. Since in the STEX approach only one-electron excitation processes are considered, we may then consider the missing theoretical intensity around 406-407

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2. Electronic structure and charge transfer effects in porphyrin arrays The afterward introduced chemical changes leading to Pt-ZnPf1, Pt-ZnPf2 and Pt-ZnPf3, were on purpose intended to give rise to supramolecular arrays. These multinuclear complexes contain one or two porphyrin molecules linked by chemical bonds and bring to an increased electron delocalization along the main chain connecting the metal centers. From this basis we expected variations on the charge density around the metal sites and at the nitrogens that, from a chemical point of view, should give the most significant evidence for this effect. Indeed, the XPS investigations of the porphyrin arrays gave indication for charge transfer occurring from the nitrogens to the inorganic sites and focused at the central metal (Pt). The linkage achieved through chemical bonding between units, by means of the on purpose introduced ethynyl groups in meso position, preserved the π orbital electron conjugation pathway, permitting charge mobility; in addition the bonding between the inorganic centers (i.e. the Pt metal center) and the ethynyl groups involved orbitals p and d in character, thus producing an extended overlap also accounting for charge mobility alongside [22]. Conjugation increase causes splitting in the π and π* levels, reducing the HOMO-LUMO gap and the manifestation of this are a red shift of electronic spectra or shift and enhancement of the XPS shake up satellites. Evidence for the increased conjugation capability has been searched as well by NEXAFS spectroscopy at the nitrogen K-edge. We observed that throughout the series of porphyrin complexes a continue shift of the C-N σ* features occurs. The increase in energy of the σ* resonances, that reaches values as high as nearly 1 eV, only partially originates by chemical shift, whereas mostly rely to additional effects. In fact, we believe that for the multiporphyrins complexes, compared with ZnPf2, the trend for the σ* resonances is associated to a bond shortening (CN) which in turns is an indication of larger orbital overlap and therefore, increasing conjugation capability in the larger systems where -PtCl(PR2)2 tethers are involved. 3. Porphyrin-fullerene hybrids One more advance in the knowledge of the porphyrins behaviour and properties was searched in the assembling of new supramolecular structures with the intent of investigating the frontiers of improved peculiar properties of porphyrins. Bearing in mind this endeavor, we have attempted a mixed porphyrin-fullerene assembly. The experimental results, hereafter reported in detail, led to the evidence that the building of a mixed Pf-C60 hybrid produce a slight charge transfer from the electron

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rich fullerene to the porphyrin (ZnPf2) and that the geometrical arrangement of the porphyrin, which varies upon increasing the coverage, is well suited to allocate fullerene molecules in stack-layered configuration. The hybrid has been prepared in situ, in order to avoid interferences and therefore, clearly understand the introduced modifications. The experimental observations re-

the fullerene coverage. Evidence for C60 spheres diffusion into the porphyrin layers was given by the SR-induced XPS at the C1s core level: such an effect can take place if there is enough space to accommodate the incoming species and strongly depending on the occurrence of attractive forces in the inside. In Fig. 6 a representation of the hybrid Zn-porphyrin/C60 is displayed.

Figure 5. The geometry of 2,8,12,18-tetraethyl-5,15-diethynyl-3,7,13,17tetramethylporphyrinatozinc(II) (ZnPf2) molecular arrangement when growing on the Cu(111) surface is shown. In the upper panel the condition of flat lying (submonolayer) is abandoned as the coverage increases and molecules start tilting up. In the lower panel the situation at the monolayer and also in the multilayer regime is depicted, with the ZnPf2 molecules oriented and standing stacked at 80° nearly perpendicular to the Cu surface.

Figure 6. The geometry for the porphyrin/fullerene hybrid (ZnPf2/C60), as hypothesized from the NEXAFS and XPS experimental observations, is depicted. Fullerene C 60 sphere after diffusion into the multilayer ZnPf2, is facing with the π-bonds two parallel Zn-porphirinato planes at the chromophore level.

garding the molecular arrangement of ZnPf2, as derived by the angular dependent NEXAFS measurement at the N K-edge, can be summarized as follows. As the porphyrin molecules approach the copper surface they set lying flat but, as soon as they get in close vicinity to each other, they rise up in a nearly perpendicular fashion. The interplay between intermolecular forces and substrateadsorbate interaction play the major role in the molecular organization in solid state. In the present case, the intermolecular forces are strikingly overcoming the second ones, by increasing the coverage, thus giving rise to a progressive tilt of the porphyrin surface plane towards a nearly perpendicular geometry, relative to the substrate. At the monolayer completion a preferential molecular orientation occurs giving rise to order and parallel molecular arrangement (stacked); much fascinating, this molecular arrangement is preserved in the multilayer regime. The change from a flat to a nearly standing geometry is depicted in Fig. 5. Zn-porphyrin multilayer sample was interfaced with fullerene C60 and the changes monitored as a function of

Experimental evidence, by SR-XPS and NEXAFS, for the interaction between the species is given by the charge density modification at the porphyrin chromophore and mainly reflected in the increase of the ionization potential at the N1s core level [23]. A minor, but to a great extent considerable effect, is also detected in the secondary N1s structure; the shake up satellite shifts towards the main line and at the same time undergoes enhancement. The overall interpretation takes into consideration that each electron rich fullerene accommodate in between two standing porphyrin planes, with the double bonds facing the electropositive chromophore center of the porphyrins to a distance of about 2.6-3.0 Å. This distance is notably shorter than the separation of π-π interactions [24]. Graphite and thypical arene/arene separations are in the range 3.3-3.5 Å; interfacial porphyrin-porphyrin separations are larger than 3.2 Å; fullerene-arene approaches lie in the range 3.0-3.5 Å, and fullerenefullerene separation are typically about 3.2 Å. From these data we can figure out that in addition to a π-π interactions there must be a further bonding effect. Indeed,

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the above discussed charge transfer outcome, involving the electropositive porphyrin center, has to be relied to such an effect. The shake up modifications must be associated to both, the decrease of the HOMO-LUMO energy gap, probably induced by rising the HOMO, and porphyrin and C60 orbital mixing.

Conclusions Synchrotron Radiation spectroscopy studies, XPS and NEXAFS, allowed expounding the chemical and electronic structure of porphyrin related molecules beyond the traditional chemico-physical characterizations. The studies were performed considering a step-by-step route that starting from the simplest porphin Pf, through the more and more complicated PfNH, ZnPf1 and ZnPf2, arrived to consider the multinuclear complexes Pt-ZnPf1, Pt-ZnPf2, Pt-ZnPf3. The presence of electron donor groups linked to the porphyrin ring in PfNH enhances the electron density at the nitrogens that are chemically identical two by two. The formation of coordination compounds, by insertion of a metal such as Zn in the tetrapyrrolic ring, i.e. of ZnPf1 model molecule and of ZnPf2, leads to the situation of four equivalent nitrogens, detected by XPS and NEXAFS experiments and supported by theoretical calculations. The link of Pt coordination tethers as ending groups to the porphyrin, performed trough ethynyl bonds, provokes an electron release toward the transition metal and this effect of charge transfer is more pronounced in the case of the molecules containing diporphyrin bridging moieties, i.e. Pt-ZnPf2 and Pt-ZnPf3. Some peculiar properties of porphyrin/fullerene hybrids have also been elucidated by means of XPS and NEXAFS experiments. It has been assessed that electron transfer from C60 to ZnPf2 occurs together with a progressive insertion of C60 spheres sandwiched between the porphyrin molecular planes. The porphyrins molecules are lying flat in the submonolayer range, while tilt up progressively when getting in close vicinity and arrange nearly perpendicular to the surface of the substrate, in a stack-layer structure, at monolayer completion preserving this configuration also in the multilayer regime. This molecular arrangement implies a closer interaction than a simple π-π contact between the porphyrin ring and the fullerene producing a charge transfer C60→ZnPf2, as experimentally evidenced.

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Acknowledgements I am very pleased to acknowledge all the people that were involved in this research project, particularly M.V. Russo (University La Sapienza Rome), V. Carravetta (CNR-IPCF Pisa), A. Ferri (University La Sapienza Rome), C. Battocchio (INFM-OGG Grenoble), A. Goldoni (Elettra, Trieste), G.Iucci (University Roma Tre).

References 1. M.R. Wasielewski, Chem. Rev., 92, 435 (1992). 2. D.G. Johnson, M.P. Niemczyk, D.W. Minsek, G.P. Wiederrecht, W.A. Svec, G.L. Gaines III, M.R. Wasielewski, J. Am. Chem. Soc., 115, 5692 (1993). 3. L. Karki, F.W. Vance, J.T. Hupp, S.M. LeCours, M.J. Therien, J. Am. Chem. Soc. 120, 2606 (1998). 4. H.L. Anderson, S.J. Martin, D.D.C. Bradley, Angew. Chem. Int. Ed.Engl., 33, 655 (1994) 5. S. Priyadarshy, M.J. Therien, D.N. Beratan, J. Am. Chem. Soc. 118, 1504 (1996). 6. J. Seth, V. Palaniappan, T.E. Johnson, S. Prathapan, J.S. Lindsey, D.F. Bocian, J.Am. Chem. Soc., 116, 10578 (1994). 7. S. Prathapan, T.E. Johnson, J.S. Lindsey, J.Am. Chem. Soc., 115, 7519 (1993). 8. J. Wojaczynski, L. Latos-Grazynski, Coord. Chem. Rev., 204, 113 (2000). 9. J. Deisenhofer, O. Epp, K. Miki, R. Huber, H. Michel, J. Mol. Biol., 180, 385 (1984). 10. V.S.-Y. Lin, S.G. Di Magno, M.J. Therien, Science, 264, 1105 (1994) 11. M.D. Ward, Chem.Soc. Rev., 26, 365 (1997). 12. I. Tabushi, S. Kugimiya, M.G. Kinnaird, T. Sasaki, J. Am. Chem. Soc., 107, 4192 (1982). 13. L.M. Proniewicz, J. Odo, J. Goral, C.K. Chang, K. Nakamoto, J. Am. Chem. Soc., 111, 2105 (1989). 14. Y. Sun, T. Drovetskaya, R.D. Bau, P.D.W. Boud, C.A. Reed, J. Org. Chem., 62, 3642 (1997). 15. A. Ferri, G. Polzonetti, S. Licoccia, R. Paolesse, D. Favretto, P. Traldi, M.V. Russo, J. Chem. Soc. Dalton Trans., 4063 (1998). 16. G. Polzonetti, A. Ferri, M.V. Russo, G. Iucci, S. Licoccia, R. Paolesse, J. Vac. Sci. Technol. A 17, 832 (1999). 17. G. Polzonetti, V. Carravetta, G. Iucci, A. Ferri, G. Paolucci, A. Goldoni, P. Parent, C. Laffon and M.V. Russo, Chem. Phys., 296, 87 (2004). 18. H. Ågren, V. Carravetta, O. Vahtras, L.G. M. Pettersson, Chem. Phys. Letters, 222, 75 (1994). 19. S. Narioka, H. Ishii, Y. Ouchi, T. Yokoama, T. Ohta, K. Seki, J. Phys. Chem., 99, 1332 (1995). 20. J. Stöhr, NEXAFS Spectroscopy, Springer, Berlin, 1992 and references therein. 21. A. Ghosh, J. Fitzgerald, P.G. Gassman, J. Almlöf , Inorg. Chem., 33, 6057 (1994). 22. H.L. Anderson, Chem. Comm., 2323 (1999). 23. G. Polzonetti, C. Battocchio, A. Goldoni, R. Larciprete, V. Carravetta, M.V. Russo, Chem.Phys., 297, 307 (2004). 24. P.D.W. Boyd, C.A. Reed, Accounts Chem. Res., 7.3 (2004) in press.

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Paper received March 2005

A NEW HIGH-ENERGY NEUTRON BEAM FACILITY IN UPPSALA A. V. Prokofiev1, S. Pomp2, J. Blomgren2, O. Byström1, C. Ekström1, O. Jonsson1, D. Reistad1, U. Tippawan2, 3, D. Wessman1, V. Ziemann1, and M. Österlund2 1 The Svedberg Lab, Uppsala University, Box 533, S-751 21 Uppsala, Sweden tel. +46-70-326-3866; fax: +46-18-471-3833;

e-mail: Alexander.Prokofiev@tsl.uu.se 2 Department of Neutron Research, Uppsala University, Sweden 3 Fast Neutron Research Facility, Chiang Mai University, Thailand

Abstract A new quasi-monoenergetic neutron beam facility has been constructed at The Svedberg Laboratory (TSL) in Uppsala, Sweden. Key features include an energy range of 20 to 175 MeV, high fluxes and the possibility of large-area neutron fields. The new facility has been designed specifically to provide optimal conditions for testing of single-event effects in electronics. First results of the beam characterization measurements are reported.

wanted. Similar effects causing hardware damage have recently been identified also on ground level. Testing of SEE using the natural flux of cosmic neutrons is timeconsuming. To speed up the measurements, one needs to use neutron beams produced with particle accelerators. The procedures for the accelerated testing of memory devices are summarized in the recent JEDEC standard [6]. According to this standard, one of the ways to perform the accelerated testing is to irradiate a device under study by monoenergetic neutrons with nominal energies of 20, 50, 100, and 150 MeV. Such an approach is a viable alternative to the testing with a “white” neutron spec-

Scientific and technical background The interest in high-energy neutrons is rapidly growing, since a number of potential large-scale applications involving fast neutrons are under development, or have been identified. These applications primarily fall into three sectors: nuclear energy and waste, medicine and effects on electronics. The recent development of high-intensity proton accelerators has resulted in ideas to use subcritical reactors, fed by external spallation-produced neutrons, for transmutation of waste from nuclear power reactors or nuclear weapons material. This might result in less problematic waste material and/or energy production; see, e.g., Ref. [1]. Conventional radiation treatment of tumors, i.e., by photons or electrons, is a cornerstone in modern cancer therapy. Some rather common types of tumors, however, cannot be treated successfully. For some of these, very good treatment results have been reached with neutron therapy, which is the largest used non-conventional therapy worldwide [2, 3]. It has been established during recent years that air flight personnel receives among the largest radiation doses in civil work, due to cosmic-ray neutrons. This poses a relatively new dosimetry problem, which is currently under investigation [4]. During the last few years, it has become evident that electronics in aircraft suffer effects from cosmic-ray neutrons, so-called single-event effects (SEE) [5, 6]. The presently most well known effect is that a neutron can induce a nuclear reaction in the silicon substrate of a memory device, releasing a free charge, which in turn flips the memory content. This random re-programming is obviously not

Figure 1. Drawing of the new neutron beam facility. The neutron beam is produced in the lithium target and continues along the D-line. The lithium target, the deflecting magnet, and the collimator are indicated. The drawing shows also the position for two permanent but movable experimental setups, Medley and SCANDAL.

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trum, if the intensity of monoenergetic neutrons is enough to cause reasonably high SEE rates. Finally, fundamental nuclear physics with intermediateenergy neutrons has recently got widespread attention due to the experimental studies of the absolute strength of the strong interaction in the nuclear sector, derived from neutron–proton scattering data; see, e.g., Ref. [7]. All the applications mentioned above involve neutrons at much higher energies than for the traditional applied areas, e.g., nuclear power. Extensive evaluated data libraries have been established for the development of nuclear fission and fusion for energy production, which have a 20 MeV upper limit. Very little high-quality neutron-induced data exist above this energy. To satisfy these needs, a new quasi-monoenergetic neutron-beam facility has been constructed at the The Svedberg Laboratory (TSL), Uppsala. Emphasis has been put on high neutron beam intensity in combination with flexibility in energy and neutron field shape. Technical specification The facility uses the 7Li(p,n)7Be reaction (Q=-1.64 MeV) to produce a quasi-monoenergetic neutron beam. The proton beam is provided by the Gustaf Werner cyclotron with an energy variable in the 20-180 MeV range. A drawing of the neutron-beam facility is shown in Fig. 1. The proton beam is incident on a target of lithium, enriched to 99.99% in 7Li. The available targets are 1, 2, 4, 8, and 24 mm thick. The targets are rectangular in shape, 20x32 mm2, and are mounted in a remotely controlled water-cooled copper rig. An additional target position contains a fluorescent screen viewed by a TV camera, which is used for beam alignment and focusing. Downstream the target, the proton beam is deflected by a magnet into a 10-m long dumping line, where it is guided onto a heavily shielded water-cooled graphite beam dump. The neutron beam is formed geometrically by a cylindrically shaped iron collimator block, 50 cm in diameter and 100 cm long, with a cylindrical, conical or rectangular hole of variable size. The collimator is surrounded by concrete to form the end wall of the production line towards the experimental area. Thereby, efficient shielding from the production target region is achieved. A modular construction of the collimator allows the user to adjust the diameter of the neutron beam to the needs of a specific experiment. The available collimator openings are 1, 2, 3, 5.4, 10, 15, 20, and 30 cm. Other collimator diameters in the 0-30 cm range, as well as other shapes than circular can be provided upon request. Beam diameters of up to 1 m are obtainable at a larger distance from the production target, which may be used for testing a larger number of devices simultaneously, or larger devices like entire electronic boards. The facility is capable to deliver neutrons

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Figure 2. Measured proton energy vs. time-of-flight (TOF) for a peak neutron energy of 74.8 MeV registered at a scattering angle of 20 degrees (see text).

in the 20-175 MeV range. This makes TSL the only laboratory in the world offering full monoenergetic neutron testing according to the JEDEC standard [6]. Neutrons reach the experimental area at a distance of about 3 m from the production target. Reduction of this distance has led to an increase of the neutron flux by about one order of magnitude in comparison with the old TSL neutron facility [8, 9], using the same target thickness, proton energy and current. Beam currents of up to 10 µA can be achieved for energies below 100 MeV. Above 100 MeV, the achievable beam current is about a factor of 10 lower. The resulting lower neutron fluence can be partly compensated by the use of thicker lithium targets. Two additional irradiation positions, which can be used parasitically with other experiments, are provided (see Table I). The increase of the neutron flux at these positions is reached at the expense of limited accessibility, limited size of irradiated objects, and more intense γ-ray background.

Position

Distance from the Li target (m)

Angle to the proton beam direction (°)

PARTY

1.9

1.6

2.5

TUNIS

1.1

7.5

1.7 – 2.21)

dependent on the peak neutron energy.

Table I. Parasitic irradiation positions.

Gain in the peak neutron flux

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Neutron Energy (MeV) Figure 3. The neutron spectra at 0º for different peak neutron energies (see Table II for incident proton energies and 7Li target thicknesses). Symbols connected by a solid line represent experimental data obtained in the present work. Predictions are shown as dashed lines (see text).

Figure 4. The horizontal beam profile for 142.7-MeV neutrons, measured at the distance of 4.77 m from the production target. Vertical dashed lines represent boundaries of the beam expected from the geometry of the collimator.

Characterization of the facility The first neutron beam at the new facility was delivered in 2004. Since then, commissioning runs have been performed, including measurements of neutron flux, spectra, and profile. First results are reported below. The measured contamination of the neutron beam at the experimental area due to interactions of the primary protons with beam transport elements such as the target frame did not exceed 0.2%. Such interactions only leads to a minor surplus of neutrons in the experimental area because charged particles produced near the lithium tar-

get and upstream are removed by the deflection magnet. The relative contamination of protons with energies above 15 MeV in the neutron beam is about 10?5. These measurements have been performed for a proton beam energy of 98 MeV. The energy and angular distribution of neutrons delivered to the experimental area is mainly defined by the double-differential cross-section of the 7Li(p,n) reaction at forward angles. The reaction energy spectrum is dominated by a peak situated a few MeV below the energy of the primary protons and comprising about 40% of the

Proton beam energy (MeV)

Li target thicknes s (mm)

Proton beam current (µA)

24.68 ± 0.04 49.5 ± 0.2 97.9 ± 0.3 147.4 ± 0.6

2 4 8 24

10 10 5 0.6

Resulting average energy of peak neutrons (MeV)

Fraction of neutrons in Peak neutron flux the mono-energetic peak (%) (105 neutrons/(cm2 s)) _______________________________ measured calculated

21.8 46.5 94.7 142.7

~50 39 41 55 1)

-36 39 40

1.3 2.9 4.6 2.1

upper limit due to poor energy resolution.

Table II. Neutron beam parameters. The fluxes refer to the entrance of the beam line to the experimental hall.

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total number of neutrons. Neutron spectra have been obtained by measuring elastic np-scattering with the Medley setup [10]. The scattered protons are registered at an angle of 20° relative to the neutron beam. Besides the energy of the scattered proton, the time-of-flight (TOF) relative to the RF signal from the cyclotron for each event is recorded. As an example, the measured proton energy vs. neutron TOF is shown in Fig. 2. All proton events for a peak neutron energy of 74.8 MeV are contained. The horizontal and vertical straight lines indicate the position of the proton peak in time and energy for elastic scattering events caused by peak neutrons. The bent line shows the calculated position of elastic scattering events for different neutron energies. The neutron spectrum is deduced by application of a cut around this bent line, proper background subtraction and calculation of the corresponding incoming neutron energy on an event-by-event basis. The measured neutron spectra for four peak energies between 21.8 and 142.7 MeV are shown in Fig. 3. The peak energies are chosen in compliance with recommendations of the JEDEC standard [6]. The measurements are compared with the systematics by Prokofiev et al. [11] for the three higher energies (Fig. 3 b-d). The systematics is not applicable at the lowest beam energy (Fig. 3 a). Instead, an evaluation of Mashnik et al. [12] was employed for the description of the neutron spectrum. The differential cross-section for high-energy peak neutron production at 0° was obtained by multiplication of the total crosssection of the 7Li(p,n)7Be reaction [12] to the “index of forwardness” from the systematics of Uwamino et al. [13]. The narrow peaks in the upper continuum region correspond to excitation of higher states in residual 7Be nuclei. This process was included in the model calculation of Mashnik et al. [12]. However, the energy resolution in the experiment does not allow us to observe these peaks. The experimental data agree with the calculations except for the region below 10 MeV in the 21.8 MeV spectrum where the model overpredicts the experimental results by up to a factor of 2. Table II summarizes the main features of the measured spectra and the achieved neutron flux. The later has been measured with the thin-film breakdown counter (TFBC) [14]. Another monitoring option is provided by an ion-

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ization-chamber monitor (ICM). Both monitors, usually installed after the Medley chamber, utilize neutron-induced fission of 238U. Finally, a Faraday cup, installed in the proton beam dump, integrates the beam current and offers relative monitoring of the beam intensity. Figure 4 shows a horizontal beam profile for 143 MeV neutrons, measured at a distance of 4.77 m from the production target. The measurement was performed by counting neutron-induced SEE in a set of electronic chips positioned across the beam [15]. Summary and outlook A new neutron beam facility has been constructed at TSL and is now available for regular operation. It is capable to deliver neutrons in the 20-175 MeV range. First beams have been delivered for nuclear physics research, as well as for commercial electronics testing. Acknowledgements We would like to thank all the staff at The Svedberg Laboratory for the excellent work in building this new facility. We are thankful to M. Olmos for providing us with the beam profile data. References 1. A. Koning, et al., High and Intermediate energy Nuclear Data for Accelerator-driven Systems (HINDAS), J. Nucl. Sci. Technol. 2, 1161 (2002). 2. R. Orecchia, et al., Eur. J. Cancer 34, 459 (1998). 3. D.L. Schwartz, et al., Int. J. Radiat. Oncol. Biol. Phys. 50, 449 (2001). 4. D.T. Bartlett, et al., Radiat. Res. Congress Proceedings 2, 719–723 (2000). 5. Single-Event Upsets in Microelectronics, topical issue, edited by H.H.K. Tang and N. Olsson [Mater. Res. Soc. Bull. 28 (2003)]. 6. JEDEC Standard. Measurements and Reporting of Alpha Particles and Terrestrial Cosmic Ray-Induced Soft Errors in Semiconductor Devices. JESD89, August 2001. 7. J. Blomgren (Ed.), Proceedings of Workshop on Critical Issues in the Determination of the Pion-Nucleon Coupling Constant, Physica Scripta, T87, 2000. 8. H. Condé, et al., Nucl. Instrum. Methods Phys. Res. A 292, 121 (1990). 9. J. Klug, et al., Nucl. Instrum. Methods Phys. Res. A 489, 282 (2002). 10. S. Dangtip, et al., Nucl. Instrum. Methods Phys. Res. A 452, 484 (2000). 11. A.V. Prokofiev, et al., J. Nucl. Sci. Techn., Suppl. 2, 112 (2002). 12. S.G. Mashnik, et al., LANL Report LA-UR-00-1067 (2000). 13. Y. Uwamino, et al., Nucl. Instrum. Methods Phys. Res. A 389, 463 (1997). 14. A. N. Smirnov, et al., Radiat. Meas. 25, 151 (1995). 15. M. Olmos, priv. comm.

RESEARCH INFRASTRUCTURES Paper received May 2005

ULTRA-SMALL-ANGLE NEUTRON SCATTERING (USANS): RECENT PROGRESS IN THE TECHNIQUE AND APPLICATION Michael Agamalian Spallation Neutron Source Division,

Oak Ridge National Laboratory, Bldg 8600, Oak Ridge, TN 37831-6474, USA

Abstract Being introduced to the small-angle scattering community about 6 years ago at the SAS99 International Conference USANS still remains untested by the majority of users and is still under the category “new techniques”. On the other hand, all conventional high resolution pin-hole SANS instruments worldwide are 2-3 times oversubscribed serving the largest group of neutron scatterers publishing over several hundred scientific papers per year. The mentioned discrepancy becomes mysterious after a brief analysis of numerious recent SANS publications made by the author who surprisingly found that more than a half of these studies are handicapped with the absence of data beyond the Q-resolution limit of conventional SANS diffractometers. The present review is prepared as a consequence of this “discovery” and thus should be considered as an additional guideline for the USANS technique application following with selected attractive results.

crystal and, as a consequence the rocking curve of the DCD, has extremely narrow angular resolution. This fact provides an opportunity for measuring the USANS from a sample placed in between the monochromator and analyzer crystals of the DCD; the scattered radiation can be obtained as a difference between two rocking curves measured with and without the sample under study. However, the single-bounce reflectivity curve contains also rather intense tails (or wings), which significantly decrease the Signal-to-Noise ratio (SNR) of the DCD and as a result diminishes sensitivity to small-angle scattering, because it occurs in the range of the wings. U. Bonse and M. Hart, who pioneered the remarkable “tailless single-crystal reflection” technique [3] based on application of the channel-cut multi-bounced crystals, solved this problem in the middle 1960s. The new technique originally developed for X-rays immediately gave rise to Ultra-Small-Angle X-ray (USAXS) experimental studies [4]; however the first attempts to adapt it for neutrons made in the middle 1980s at Jülich, Germany, had limited success [5]. The Bonse-Hart technique was properly applied for neutron small-angle experiments by the end of 1990s after several successful neutron dynamical diffraction experiments [6-10] carried out at the High Flux Isotope Reactor (HFIR), ORNL. As a result the signal-to-noise ratio of the ORNL neutron DCD equipped with the triplebounce Si(111) channel-cut crystals was increased by over three orders of magnitude compared to the singlebounce version of the DCD. This dramatic improvement of the SNR extended the upper limit of the dynamical length-scale range of the SANS studies by two orders of magnitude creating a real breakthrough to the neutron diffraction analysis of micrometric supra-atomic structures. Over twenty user groups immediately started scientific experiments at the ORNL USANS facility in spite of the fact that its neutron flux was not optimized. Several important scientific results were obtained examining the µm-scale structures of polymer blends [11], colloidal crystals [12, 13], rocks [14, 15], hydrating cement paste [16], reinforcing fillers [17], wormlike micelles [18] and colloidal gels [19]. The most important achievement, discovery of the enormously extended (over three orders of magnitude in the length scale) surface fractal structure in sedimentary rocks, was highlighted in Physical Review Focus [20] and in Science [21]. The breakthrough to the micrometric scale range of

Breakthrough to the Micrometric Size Structures During the past six years Ultra-Small-Angle Neutron Scattering (USANS) has emerged as a powerful new technique, which extends the dynamic range of supramolecular structural investigations two orders of magnitude beyond what has been customarily accessible. Nowadays the experimentally measurable range of neutron molecular scattering corresponds to the range of internal diffraction distances in condensed matter from ~ 10 Å to ~10 µm. Thus the multilevel supra-molecular structure of liquids and solids containing not only nanometrical particles but also aggregates and agglomerates can be described by analyzing neutron diffraction data. It is obvious that such a broad dynamic range cannot be covered by one neutron diffractometer; the conventional 30m pin-hole geometry SANS instrument [1, 2] must be coupled with a USANS apparatus. The 30m SANS machine operates effectively in the range of diffraction distances from ~500-600 Å to ~10 Å. The upper limit of this range in real space corresponds to the smallest value of scattering vector or angle in reciprocal space, thus ultrahigh angular resolution is required to extend the conventional SANS range in the direction of larger diffraction distances. The currently best approach for achieving the highest resolution in reciprocal space is related to application of the classical Double-Crystal Diffractometers (DCD) on single crystals to the USANS measurements. It is well known that the reflectivity function of a single

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neutron diffraction structural analysis was reported at the USANS session of the 11th International Conference on Small-Angle Scattering (SAS99), which was held at Brookhaven National Laboratory, USA. In the next several years the ORNL experience was used to upgrade the Bonse-Hart USANS instruments in Japan (Japanese Atomic Energy Institute) [22, 23], Germany (GKSS Forschungszentrum, Geesthacht, Berlin Neutron Scattering Center, FRJ-2, Jüelich) [24-26] and France (Institute of Laue-Langevin, Grenoble) [27]. A new fully optimized Bonse-Hart USANS facility [28, 29] equipped with the double-focused pre-monochromator was developed at the National Institute of Standards and Technology and became available for the user community in 2000. The fast progress in the USANS instrumentation was followed by growth of the international user community and number of scientific meetings and publications related to this technique. In July 2003 the International Consortium on Ultra-Small-Angle Scattering (IConUSAS) was organized at The First Workshop on Ultra-Small-Angle X-Ray & Neutron Scattering [30]. Nowadays the diffraction analysis of large structures has found broad application in materials and polymer science, colloidal chemistry, petrology, geology, industrial science and technology. Application of USANS has recently been summarized and discussed in the review papers [31, 32] and lectures delivered at the 2004 School Francesco Paolo Ricci Neutron Scattering School [33]; however, the fast-growing USANS user community needs more information about advances and consumption of this technique. The author hopes that this paper will help new users to obtain sufficient general impression about the current status and capabilities of the Bonse-Hart USANS technique.

P. Debye and A. M. Bueche [34] have shown in their classic study that atomic diffraction converts to molecular scattering when the wavelength of radiation exceeds the inter-atomic distance of a material under study. This effect gives an opportunity to study the supra-molecular structure of condensed matter in the range of Q-values ~10-6 < Q < 10-1 Å-1 (see Fig. 1). Because the typical wavelength range for X-ray and neutron molecular scattering instruments is 1 < λ < 15 Å, the corresponding diffraction angle becomes small, θ < 1o, and this is the reason why we are dealing with Small- and Ultra-Small- Angle X-ray and Neutron Scattering (SAXS, USAXS and SANS, USANS).

Supra-molecular Structural Analysis with SANS/USANS In basically all structural investigations dealing with the diffraction technique the measurements of scattered radiation are carried out in reciprocal space and all diffractometers measure the length of the scattering vector Q=4πsinθ/λ, where θ is the diffraction angle and λ the wavelength of a chosen type of radiation. The dimension of the Q-vector or the distance in reciprocal space is [length-1] and the corresponding distance in real space, or so-called diffractometric resolution, D, can be estimated as D = 2π/Q [length]. Thus, the real space image of an object under study can finally be obtained by analyzing the diffraction pattern. The ability of this technique to characterize materials with atomic-scale resolution definitely is one of the major accomplishments of the 20th century. However, not only the atomic but also molecular and supra-molecular structure of condensed matter can be studied with X-ray and neutron diffraction, as well as with light scattering.

Small Angle Diffraction became more important approximately in the 1970s when the majority of structural investigations in many important scientific fields such as materials and polymer science, biology, industrial science, colloidal and organic chemistry, and complex liquids started to shift to the supra-atomic length-scale. Nowadays conventional 30m SANS diffractometers are highly oversubscribed at all major neutron scattering laboratories as are the SAXS and USAXS instruments at the synchrotron centers. Over several hundred papers related only to neutron supra-molecular structural studies are published in popular refereed scientific journals every year, a fact which clearly shows an extremely high interest the nano-metric level of structural organization of condensed matter. This interest can easily be explained by the broad application of polymers, colloids and dispersive materials in contemporary industry and technology. It is also worthwhile to underline the exclusive importance of the SAXS/SANS analysis for the de-

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Fig. 1. The dynamic ranges of molecular and atomic scattering in the real and reciprocal space.

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velopment of nano-materials. Nowadays it becomes more and more important to obtain reliable structure information at all levels of the structural organization of materials including not only atomic and nano- but also micro-metric range of distances. As follows from Fig. 1, a complete neutron diffraction structural analysis cannot be made using just one instrument. The typical Q-range of a neutron diffraction instrument is about two-three orders of magnitude. The Wide-Angle Neutron Scattering (WANS) diffractometer covers completely the Q-range of atomic scattering. However, the whole range of molecular scattering is too broad for conventional SANS instrument (see Fig. 1). In many cases it is necessary to obtain

Fig. 2. Typical scattering from polydisperce disordered systems with complex morphology.

the diffraction pattern in the range ~10-6-10-5 <Q< 0.5 Å-1 and this can be accomplished only by combining the data of SANS and USANS measurements. The range of ultra-small Q, ~ 10-5 < Q < 10-3 Å-1, provided by reactor-based Bonse-Hart USANS instruments became available for systematic exploration ~6 years ago. Since then the importance of the micro-metric scale neutron diffraction analysis has been proven in many scientific studies. Such instruments are now routinely available at all major neutron scattering laboratories and have found fast growing applications in supra-molecular structural studies of polymers, colloids, complex and super-critical liquids, ceramics, gels, rocks, dispersive materials and other objects important for industry and technology. The combined SANS and USANS data cover the range of molecular scattering, 10-5 < Q < 0.5 Å-1, providing a great deal of structural information for systems containing inhomogenieties with dimensions ~ 10 < D < 0.1 µm. It was estimated that the presence of large-size

inhomogenieties is an issue in over 50 % of SANS studies and that is why the number of combined SANS/USANS experiments has grown so rapidly. The Bonse-Hart USANS technique, as discussed in [31], has been found exclusively effective in studies of hierarchical supramolecular structures having complicated internal organization at micro- and nanometric length scales. This interesting class of systems usually has polydisperse disordered morphology and thus the corresponding typical small-angle scattering have profiles shown in Fig. 2. The intensity vs. dimensionless parameter QRg (where Rg is the mechanical radius of gyration) contains the Porod range, QRg << 1 sensitive to the shape and the surface roughness of scattering particles. Analyzing this part of SANS/USANS data one can distinguish three dimensional (3D) inhomogenieties with smooth surface corresponding to the power law Q-4, 1D particles (Q-1), 2D particles or polymer coils (Q-2), mass fractals (Q-1 – Q-3) and surface fractals (Q-3 – Q-4). The Guinier range, QRg >> 1, or the upper cut-off of the scattering function from such kind of systems contains the information about the volume fraction, average size and contrast of ingomogenieties. A detailed analysis of the combined USANS/SANS data can be done by modeling the diffraction pattern in terms of the form-factor, F(QR), of the scattering particle, the size distribution function, N(R), and the interparticle correlation function, S(QD). Several interesting studies of hierarchical structures are discussed below. Self-similarity of Rocks Owing to the limited size range over which fractal properties are usually observed, the issue of the apparent fractal geometry of various natural objects is a contentious one. In their critique of 96 recent reports on the fractality of a wide range of physical systems, Avnir et al. pointed out the contradiction between the narrow range of the appropriate scaling properties for declared fractal objects (centered around 1.3 orders of magnitude) and the public image of the status of experimental fractals [35], which for rocks has previously been based on limited experimental evidence (about 1.5 decades in length scale). A notable exception is the x-ray study of Bale and Schmidt on coals [36] showing fractality of pore boundaries extended over 2 decades in length scale and 7.5 decades in the intensity of combined USANS/SANS intensity. Various other studies performed on rocks of different origin and lithology also show that rocks are often effective fractals extended over length scales from 20 Å to 100 µm. Small-angle X-ray and neutron scattering as well as molecular adsorption and real imaging techniques are effective tools of these important studies. In our chosen example of a combined USANS/SANS study on sedimentary rocks [14] USANS provides the majority of structural in-

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formation clearly showing its necessity in this class of structural investigations. A. P. Radlinski and co-authors have demonstrated in this remarkable study that the surface fractals of rock-pore interface cover over 3 decades of the length scale showing that sedimentary rocks are in fact one of the most extensive fractal systems found in nature [20-21]. The SANS instrument D11 at ILL (λ= 4.5, 7 and 14 Å), the USANS (λ = 2.59 Å) and 30-m SANS (λ = 4.75 Å) facilities at ORNL covering the Q-range, 2·10-5 < Q < 0.3 Å-1, were used to obtain diffraction data from a specimen of hydrocarbon source rock U116 [37]. The region of the power-law scattering in Fig. 3 extends over 3 orders of magnitude of the length scale (60 Å ≤ 2π/Q ≤ 6 µm) and 10 orders of magnitude of the scattering cross section (10-1 ≤ dΣ/dΩ ≤ 109 cm-1). Such an extent of fractal

ing fraction of the polymer market, so these materials are the subject of intense scientific and commercial interest [38]. SANS has been used intensively by industrial scientists to investigate polymer-polymer thermodynamics, however, the high-resolution 30m SANS is unable to detect large aggregates of macromolecules, voids and µm-size admixtures in polymer blends, which can significantly alter the quality of these materials. M. Agamalian and co-authors successfully used combined USANS/SANS measurements to reveal the structure of linear and branched polyethylene blends [11]. Polyethylene (PE) constitutes one of the largest segments of the polymer market and different forms are often mixed (blended) together to improve their properties. For example, blends of linear, high density PE (HDPE) and

Fig. 4. USANS/SANS data from HDPE/HPB and HDPE/LDPE polymer blends.

Fig. 3. Combined USANS/SANS neutron scattering cross-section for rock U116.

microstructure in a rock is remarkable, in particular when compared with numerous other reports on the fractal properties of natural systems [35]. The slope of Q3.18 obtained from a straight line fit in the 10-4 ≤ Q ≤ 10-1 Å-1 region corresponds to a surface fractal of dimension Ds = - 2.82. The departure of the scattering curve from a straight line at Q < 10-4 Å-1 corresponds to the beginning of the upper cut-off range (see Fig. 2), which is below Qmin of the reactor-based USANS instrument. Polyethylene blends Because of difficulties in commercializing new polymers, industry has turned increasingly to combining (blending) existing polymers in order to optimize their end-use properties. Such materials currently account for a grow-

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long-chain branched, low density PE (LDPE) are widely used. PE is currently produced in many forms, each of which has different properties resulting from variations in structure. HDPE is the most crystalline form, because the chains contain very little branching. Typical LDPE contains both short chain branches (1-3 per 100 backbone carbon atoms), as well as long chain branches (0.1 - 0.3 per 100 backbone carbon atoms). Linear low density PE (LLDPE) is produced by co-polymerizing ethylene with an alpha-olefin such as hexene and can have a wide range of branch contents, depending on the catalyst and concentration of added co-monomer. The properties of the individual species can be altered by mixing the components, and blends of HDPE, LDPE and LLDPE. However, understanding of the mechanical and melt flow properties of such blends is handicapped by the absence of a consensus concerning the melt miscibility of the components. Conventional SANS data indicate that for HDPE/LDPE

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blends with molecular weights ~ 105 Daltons, the melt is homogenous [39], after accounting for H/D isotope effects. Similarly, mixtures of HDPE and LLDPE are homogenous in the melt when the branch content is low (i.e. < 3 br./100 backbone C). However, when the branch content is high (> 10 br./100 backbone C), the blends phase separate. It has been asserted [40] that these experiments performed with Qmin ~ 3 10 -3 Å-1 and thus do not provide unambiguous evidence for a 1-phase (homogenous) melt for HDPE/LDPE blends. The data might also be interpreted as arising from a bi-phasic melt with a very large particle size; therefore, this hypothesis has been addressed using a USANS technique. A 75/25 blend of protonated LDPE and deuterated HDPE was prepared which would be expected to be homogeneous in the melt, based on previous conventional SANS experiments. As an example of a phase separated blend, a 75/25 mixture of a highly branched hydrogenated polybutadiene (HPB) serving as a virtually monodisperse model of LLDPE and linear PE was also prepared. The combined USANS/SANS data in Fig. 4 clearly show that the phase separated blend has a very high scattering cross section [dΣ/dΩ(Q) ~ 108 cm-1] at Q ~ 2· 10-5 Å-1. Conversely, the USANS signal from the homogenous blend of HDPE/LDPE is virtually indistinguishable from unlabeled the LDPE homopolymer “blank”, which is to be expected if the blend is homogenous as concluded previously from pinhole SANS data [39]. USANS experiments have finally resolved this longstanding dispute and demonstrated homogeneity of the HDPE/LDPE mixtures on µm-length scales [11].

tered intensity remains approximately unchanged. However, the low Q-resolution of the conventional SANS instrument used in this study did not allow observation of the scattering profiles in the range of smaller Q. The USANS camera allowed the authors to estimate the cluster correlation length of this final sheared gel and to determine its power-law exponent. The gel precursor was an aqueous suspension of colloidal silica spheres with a mean diameter of 7 nm, estimated polydispersity of 20%, at a volume fraction of 30% and a pH ~ 10. Gelation was initiated by adding concentrated HCl until the pH fell to 8.0 [41]. After this initiation, the sample was placed immediately in a Couette cell and sheared at a constant rate of 500 s-1. The viscosity behavior mirrored that shown with a peak corresponding to a shear stress of 350 Pa s

Sheared Silica Gels C. D. Muzny and co-authors carried out an interesting combined USANS and conventional SANS study of reconstructing sheared colloidal silica gels [19]. In the previous work [41], the authors measured simultaneously the viscosity and the neutron scattering curve of the silica system as functions of time after gel initiation. It was demonstrated that when the specimen is subjected to a constant shear rate, the viscosity first increases after gel initiation, peaks at a shear-rate-independent threshold, and then declines asymptotically to about one-tenth of the peak value. While shearing, the intensity rose slowly with time in the range 2· 10-3 < Q < 1· 10-2 Å-1, but increased abruptly at around the moment at which the viscosity reached its maximum value; the intensity of scattering continued to rise to an effective plateau value at a time when the viscosity approached its asymptotic limit. The maximum in the viscosity, coupled with the marked variation of the intensity of scattering arises from a shear-induced densification transition in the growing clusters of colloidal silica [41]. It was noted that the system gels when the shear is removed, but that the scat-

Fig. 5. USANS/SANS profiles from a colloidal silica gel when subject to a shear during gelation (open circles) and when unsheared (open squares).

after 30 min of shearing. After 12 h, the sample was removed from the shearing cell and placed in a rectangular quartz cuvette with a 2 mm path length and allowed to gel. This final sheared gel was measured at the ORNL Bonse-Hart USANS instrument. Fig. 5 shows the desmeared USANS data for the sheared silica gel plotted with the SANS profiles measured from the sheared and unsheared specimens. The best fit (solid line in Fig. 5) was obtained from an empirical expression [42] to scale the scattering intensities from unsheared gels generated at pH < 8. The expression describes a scattering curve with a Q = 0 limit of α, a correlation peak of unit height at Q/2π = 1/ξ, and an asymptotic power-law Q-d behavior. The correlation length, ξ = 2.3 µm, and d = 2.92 were determined from the USANS experiment. The pronounced effect of shear on gelation is demonstrated unquestionably by the four order-of-magnitude difference in scattering intensity between the

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Fig. 6. USANS/SANS data from attractive glasses of PS-PAA/EA micelles. The strength of attraction f = 0.44 (strong), 0.61, 0.79 and 0.97 (week) is given in the diagram. The fluorescence microphotographs correspond to f = 0.44 (top), f = 61 (middle) and f = 0.97 (bottom); the scale bar is 100 µm.

sheared and unsheared gels in the USANS range, and the appearance of the Bragg reflection in the vicinity of Q = 4·10-4 Å-1. The diffraction peak reflects cluster–cluster correlations with the length ξ = 2.3 µm. One can compare this value with the cluster sizes of ~ 200 Å obtained for the unsheared gel [41]. Finally, Fig. 5 illustrates how the power-law slope d = 2.92 associated with the sheared gel contrasts with the low-Q intensity plateau of the unsheared gel. Since it has been shown [41] that the fractal dimension of the system immediately before gelling is about 1.4, this result confirms the hypothesis that the viscosity increase is indeed the consequence of a shearinduced cluster densification transition. Attractive Glasses M. A. Crichton and S. R. Bhatia used USANS/SANS technique along with fluorescence microscopy to demonstrate existence of none-mass-fractal large-scale aggre-

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gates in attractive colloidal glasses [43]. Colloidal glasses and fractal colloidal gels can be considered as the “arrested” state of soft matter and thus are interesting from the fundamental point of view. These systems also form emulsions and foams, which found practical application in cosmetics and foods. In colloidal gels attractive forces impart a percolated network structure initiating an elastic response; these systems can be either repulsion-driven or attraction-driven. If repulsive interparticle forces are dominant, the structural arrest occurs through caging of particles by their neighbors. Weak short-range attractions melt the glass; however, a new type of glassy state is formed when the strength of attraction is increased. In the attraction-driven glasses long-life interparticle bonds responsible for the structural arrest are formed. In this case the attractive forces are much weaker than that present in the attractive colloidal gels. Colloidal gels and glasses can exhibit similarities, which make it difficult to

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distinguish them in the rheological experiments; however, they have differences in the supramolecular structure. It is known that colloidal gels usually have a mass fractal structure with the fractal dimensions, 1.8 < dm < 2.2, depending on the mechanism of aggregation. The colloidal glasses have denser microstructures than the fractal gels and thus one should not expect existence of large-scale structures in such systems. In the present study the attraction-driven colloidal glasses were composed from poly(styrene)-poly(acrylic acid/ethyl acrylate) molecules (PS-PAA/EA), which form spherical micelles in aqueous solution. Fig. 5 shows the combined USANS/SANS data for the 4 samples with the strength of attraction, f, varies from f = 0.44 (strong attraction) to f = 0.97 (week attraction). A broad Bragg peak at Q ≈ 2·10-2 Å-1 is related to the intermicellar correlation and indicates the glassy state. The scattering curves in the range ~ 3·10-5 < Q < ~ 4·10-3 Å-1 show the power law Q-d behavior with d varies in the range, -2.9 < d < - 3.9. This range of d corresponds to the surface fractals (see Fig. 2) and this result is in a good agreement with the fluorescence microscopy images also given in Fig. 6. The strong surface roughness at f = 0.44 (top image) corresponds to the slope -2.9 and the smooth surface at f = 0.97 (bottom image) matches with the slope -3.9 (slope -4 indicates a 3D compact particle). The low-Q cutoff of the USANS data is below the Qmin of the USANS instrument because the average size of aggregates according the fluorescence microscopy data is ~ 10 – 100 µm.

USANS Instruments: Current Status and New Projects Nowadays the reactor-based Bonse-Hart USANS instrument has become routine equipment practically at all major neutron scattering laboratories; the USANS facilities are currently operational at the National Institute of Standards and Technology (NIST), USA, Japanese Atomic Energy Institute, Hahn-Meitner Institute in Berlin, and Kernforschungsanlage Jülich GmbH, Germany, Institute Laue-Langevin, France and at the Atominstitut, Austria. The world’s best BT-5 USANS at NIST [44] (see the instrument layout in Fig. 7) delivers a neutron flux of ~ 17000 n/(cm2sec) at the sample position and reaches the sensitivity I(Q=5· 10-4 Å-1) / I(Q=0) ~ 5·10-7 covering the dynamical Q-range, 3·10-5 Å-1 < Q < 2 · 10 -2 Å -1. Therefore, the Q-range of this instrument overlaps with that for the conventional pin-hole SANS facility in the broad band, 1 · 10 -3 Å -1 < Q < 2 · 10 -2 Å -1, which permits conducting combined USANS/SANS experiments even in cases of weakly scattering systems. Besides, special construction of the vibration control optical table at BT-5 allows introducing conventional SANS sample environment equipment. Oak Ridge National Laboratory (ORNL) plans to set up a new BonseHart USANS instrument at CG-4 cold neutron guide; this instrument expects to be about 5 times faster and 50 times more sensitive (~ 10-8) than that at NIST. A new concept of the multi-wavelength time-of-flight BonseHart USANS (TOF-USANS) instrument has recently been developed for pulsed neutron sources [45]. This

Fig. 7. Layout of the USANS instrument at NIST. The instrument components: sapphire filter (SF), pyrolytic graphite filter (GF), graphite premonochromator (PM), Si monochromator (M), beam monitor (BM), sample changer (S), Si analyzer (A), transmission detector (TD), vibration controlled table (T), beam apertures (AP) and main detector (MD).

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version of the double-crystal diffractometer on perfect crystals shows significant performance gain and gives an opportunity to extend the Q-resolution by an order of magnitude (see in Fig. 1) reaching Qmin ~ 2·10-6 Å-1. The first TOF-USANS instrument will be developed at the Spallation Neutron Source, which is currently under construction at ORNL.

References 1. W. Schmatz, T. Springer & J. Schelten, J. Appl. Cryst., 7, (1974). 2. C. J. Glinka, J. G. Barker, B. Hammouda, S. Krueger, J. Moyer, & W. J. Orts. J. Appl. Cryst., 31, 430, (1998). 3. U. Bonse & M. Hart, Applied Physics Letters, 7, 238, (1965). 4. U. Bonse & M. Hart, Zeitschrift für Physik, 189, 151, (1966). 5. D. Schwahn, A. Miksovsky, H. Rauch, E. Seidl & G. Zugarek, Nucl. Instrum. Methods, A239, 229, (1985). 6. M. Agamalian, G. D.Wignall & R.Triolo, J.Appl.Cryst, 30, 345, (1997). 7. M. Agamalian, D. K.Christen, A. R.Drews, C. J.Glinka, H. Matsuoka & G. D. Wignall, J.Appl.Cryst, 31, 235, (1998). 8. M. Agamalian, C. J. Glinka, E. Iolin, L. Rusevich & G. D. Wignall, Phys. Rev. Lett., (1998), 81, 602, (1998). 9. M. Agamalian, G. D.Wignall & R.Triolo, Neutron News, 9, 24, (1998). 10. M. Agamalian, E. Iolin & G. D.Wignall, Neutron News (1999), 10, 24, (1999). 11. M. Agamalian, R.G. Alamo, J. D. Londono, L. Mandelkern & G. D. Wignall. Macromolecules, 32, 3093, (1999). 12. H. Matsuoka, T. Ikeda, H. Yamaoka, M. Hashimoto, T. Takahashi, M. Agamalian & G. D. Wignall, Langmuir, 15, 293, (1999). 13. T. Harada, H. Matsuoka, T. Yamamoto, H. Yamaoka, J. S. Lin, M. Agamalian & G. D. Wignall, Colloids and Surfaces A, 190, (2001). 14. A. P. Radlinski, E. Z. Radlinska, M. Agamalian, G. D. Wignall, P. Lindner & O. G. Randl, Phys. Rev. Lett., 82, 3078, (1999). 15. F. Triolo, A. Triolo, M. Agamalian, J. S. Lin, R. K. Heenan, G. Lucido & R. Triolo. J. Appl. Cryst., 33, 863, (2000). 16. T. M. Sabine, Concrete in Australia, 75, 21, (1999). 17. D. W. Schaefer, T. Rieker, M. Agamalian, J. S. Lin, D. Fischer, S. Sukumaran, C. Chen, G. Beaucage, C. Herd & J. Ivie, J. Appl. Cryst., 33, 587, (2000). 18. Y.-Y. Won, H. T. Davis, F. Bates, M. Agamalian & G. D. Wignall., J. Chem. Phys. B, 104, 7134, (2000). 19. C. D. Muzny, B. D. Butler, H. J. M. Hanley & M. Agamalian, J. Phys.: Condens. Matter, 11, L295, (1999).

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20. D. Mackenzie. Rocks as Fractals. Phys. Rev. Focus. (1999), April 15, http://focus.aps.org/v3/st22.html 21. Fractals Spotted in Rocks. Academic Press (1999), April 19, http://www.academicpress.com/inscight/04191999/grapha.htm 22. T. Takahashi, M. Hashimoto & S. Nakatani, J. Phys. & Chem. of Solids, 60, 1591, (1999). 23. K. Aizawa & H. Tomimitsu, Physica B, 213 & 214, 884, (1995). 24. D. Bellmann, P. Staron & P. Becker, Physica B, 276, 124, (2000). 25. W. Treimer, M. Strobl & A. Hilger, Physics Letters, A 289, 151, (2001). 26. S. Borbèly, M. Heiderich, D. Schwahn & E. Seidl, Physica B, 276-278, 138, (2000). 27. M. Hainbuchner, M. Villa, G. Kroupa, G. Bruckner, M. Baron, H. Amenitsch, E. Seidl & H. Rauch, J. Appl. Cryst., 33, 851, (2000). 28. A. R. Drews, J. G. Barker, C. J. Glinka & M. Agamalian, Physica B, 241-243, 189, (1998). 29. J. G. Barker, C. J. Glinka, J. Moyer, M. H. Kim, A. R. Drews & M. Agamalian. To be submitted to J. Appl. Cryst. 30. M. Agamalian, Neutron News, 14, 11, (2003). 31. D. W. Schaefer & M. Agamalian, Current Options in Solid State & Materials Science, 8, 39, (2004). 32. F. Lo Celso, I. Ruffo, A. Riso and V. Benfane, Notiziario Neutroni e Luce di Sinchrotrone, 10, 3, (2005). 33. R. Triolo, Notiziario Neutroni e Luce di Sinchrotrone, 10, 39, (2005). 34. P. Debye & A. M. Bueche, J. Appl. Physics, 20, 518, (1949). 35. D. Avnir, O. Biham, D. Lidar & O. Malcai, Science, 279, 39, (1998). 36. H. D. Bale & P. W. Schmidt, Phys. Rev. Lett., 53, 596, (1984). 37. A. P. Radlinski, C. J. Boreham, G. D. Wignall & J.-S. Lin, Phys. Rev., 53, 14152, (1996). 38. J. Mark, K. Ngai, W. Graessly, L. Maldenkern, E. Samulski, J. Koenig & G. D. Wignall, Physical Properties of Polymers. Cambridge Univ. Press, third edition, p. 473, (2004). 39. R. G. Alamo, J. D. Londono, L. Mandelkern, F. C. Stehling & G. D. Wignall, Macromolecules, 27, 411, (1994). 40. C. Schipp, M. J. Hill, P. J. Barham, V. M. Cloke, J. S. Higgins & L. Oiarzabal, Polymer, 37, 2291, (1996). 41. H. J. M. Hanley, B. D. Butler, C. D. Muzny, G. C. Straty, J. Bartlett & E. Drabarek, J. Phys.: Condens. Matter, 11, 1369, (1999). 42. B. D. Butler, C. D. Muzny & H. J. M. Hanley, Int J. Thermophysics, 20, 35, (1999). 43. M. A. Crichton & S. R. Bhatia, Submitted to Langmuir, (2005). 44. J. G. Barker, C. J. Glinka, J. Moyer, M. H. Kim, A. R. Drews & M. Agamalian. To be submitted to J. Appl. Cryst., (2005). 45. J. M. Carpenter, M. Agamalian, K. C. Littrell, P. Thiyagarajan & Ch. Rehm, J. Appl. Cryst., 36, 763, (2003).

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Paper received May 2005

OPPORTUNITIES FOR THE STUDY OF SOFT MATTER ON THE ISIS SECOND TARGET STATION, TS-2 J. Penfold TS-2 Project Scientist, ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OXON, UK

The Second Target Station project, TS-2, at ISIS is now well into its construction phase. It will provide new neutron scattering facilities for the study of Soft Matter, Bio-Materials, Advanced Materials, and Nano-Materials. In this article I will review the recent project progress, and highlight the opportunities for the study of Soft Matter using cold neutron beams. Some recent examples using the current generation of instrumentation will be used to illustrate the progress towards realizing some of these new opportunities. Since the start of the major civil engineering work on the ISIS site to accommodate the Second Target Station in June 2003, there has been an ever increasing visual impact of the project construction work. The landscape to the south of ISIS has been transformed, and a new support building has been constructed (Fig. 1).

Many of the major contracts are now placed, and the project is on schedule to meet it’s major milestones of, ‘first proton beam to target’ in June 2007, ‘first instrument operation’ in November 2007, and ‘the start of the experimental programme’ in October 2008. The low frequency (10 hz) and relatively low operating power (48 kW) of the Second Target Station has provided the opportunity to produce a target / moderator / reflector assembly, using a combination of a coupled and a decoupled moderator, highly optimized for the production of cold neutrons (Fig. 3). The significantly enhanced cold neutron flux (compared to the existing 50 hz facility), the simultaneous access to an unprecedentedly broad spectral range, and the potential for high resolution, are all features which are highly tuned for studies in the key strategic areas of Soft

Figure 1. Recent view of the site, with the installation of the steel work for the main TS-2 building in progress.

Figure 2. Architect’s drawing of the appearance of the finished building.

The construction of the main target station and experimental building is making rapid progress (Fig. 2). The detailed design and construction of the target station monolith is making good progress, along with the other major technical components, the moderators and cryogenic systems, the target, and the proton beam line.

Matter, Bio-Materials, Advanced Materials, and Nanotechnology. The ‘day one’ instrument suite (November 2007), of seven instruments, has been chosen to maximize the impact in these key scientific areas (Fig. 4). They comprise of two surface reflectometers / diffractometers, INTER and polREF, for the study of chemical

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and magnetic surfaces and interfaces, the surface diffractometer offSPEC, for the study of surface structure, the low scattering vector diffractometer, SANS2B, to probe mesoscale structures, and the diffractometer, NIMROD, to probe near and intermediate range order, the spectrometer, LET, for the characterization of slow dynamics, and the powder diffractometer, WISH, to measure magnetic structures. They will all offer new capabilities and levels of performance compared to existing instrumentation at ISIS. These instruments are now fully funded from the UK government and the EU FP6 programme, and the detailed engineering design and procurement is now underway. Soft Matter encompasses a wide range of molecular materials, such as polymers, colloids, surfactant mesophases and emulsions. The physical and chemical properties of these systems are of increasing technological and industrial importance. They have a wide range of applications which are related to their bulk and interfacial properties, which include phenomena such as viscoelasticity and surface tension, and which control practical phenomena such as rubber elasticity, detergency, adhesion and lubrication. Current and future research interests are being increasingly motivated by the commercial significance of products that are complex mixtures of components and structures. This is an area of considerable

bio-materials, where areas such as directed or templated growth of mesoporous materials, functionalized colloidal particles, bio-sensors, bio-functional surfaces, the study of membranes and artificial bio-synthetic materials are all important. Neutron scattering, through the unique insight offered by predominantly H/D isotopic substitution, is a key structural technique. In terms of the bulk structure SANS2B and NIMROD are key instruments, and INTER, polREF, and offSPEC provide access to interfacial structures. At ISIS and elsewhere there are discernable trends towards the study of complex multi-phase or multi-component materials, the study of kinetic processes, the use of complex of difficult environments, the requirement for smaller samples, and the need for extensive parametric studies, are all evident. Extensive parametric studies (the need to make measurements over a wide range of conditions, temperature, pH, pressure, concentration, composition etc) will be possible with better resolution, in shorter times and on more dilute systems. More complex multi-component systems (more closely resembling industrially relevant materials) will be accessible, providing the opportunity to investigate the often critical role of minority components. More complex environments (relevant to the conditions in different processing routes, extruders, electro-

Figure 3. Engineering layout of the target monolith, showing the beam ports, target void vessel, and shutters.

Figure 4. Instrument layout, showing the location of the 7 ‘day one’ instruments.

growth and future potential, with links to products such as domestic and personal care products, cosmetics, drug delivery systems, adhesives, coatings, lubricants, sensors, devices and displays, tertiary oil recovery and mineral processing. Furthermore there is substantial overlap with and drive from nanotechnology, and the study of

chemical cells etc) and more complex interfaces will be accessible. Measurements of time dependent processes will open up poorly understood areas such as dynamic surface properties and the molecular origins of complex rheological phenomena Neutron reflectivity has transformed our ability to study

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Figure 5. Schematic representation of adsorption of complex surfactant mixtures at the air-solution interface in the presence of a coexisting bulk solution

QUARTZ BLOCK FILLING PORT WINDOW RESERVOIR

BEVEL SPRING

LOCKING COLLAR HYDRAULIC PRESS Figure 6. Adsorption at air-solution interface (mole fraction of nonionic surfactant) for different di-alkyl chain / nonionic surfactant mixtures, as a function of solution composition (2)

Figure 7. Schematic of cell for simultaneous reflectivity and surface force measurements in thin layers.

adsorption at interfaces (1). The recent study by Penfold et al (2) on the adsorption of di-alkyl chain cationic / nonionic surfactant mixtures (mixtures common place in products such as conditioners and shampoos) at the airsolution interface is an example of the ever increasing complexity that is becoming accessible.

The adsorption shows a complex pattern of adsorption behaviour (see Fig. 6 that is intimately linked to the solution phase, see Fig. 5). In the future simultaneous insitu measurements of both the surface and solution properties will be possible, making such studies even more relevant. In such systems surface ordering effects

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(3), and the lateral surface structure also start to become significant features, which will be increasingly important to access. Although the air / solution interface is important, the solid / solution interface and liquid / liquid interfaces are more relevant. Access to smaller sample sizes will make a wider range of solid surfaces accessible, and the liquid-liquid interface routine (4). Smaller sample sizes will make more complex environments more accessible, such as electrochemical cells, and in the study of changes in near surface structure due to confinement, pressure and flow. Extrapolating from the pioneering work using x-rays and neutron scattering in confined geometries (5), direct comparison with surface force measurements will be possible (see Fig. 7). Kinetic or time dependent processes dominate a number of important phenomena, such as foam stability, plasticizer distributions in polymer films, and the nature of polymer / polymer interfaces. The recent work by Higgins et al (6) on plasticizer and solvent ingress into polymer thin films using neutron reflectivity represents the range of times currently accessible (~ 10 seconds). To access times of less than 1 second would provide a significant advance.

Vacklin et al (7) on how phospholipase A2 enzyme catalyses the hydrolysis of phospholipids. It is a mechanism that occurs in a range of cell membrane environments, form snake venom to the immune system, and plays a key role in maintaining cell membrane composition, signal transduction and inflammatory response. In this study they have been able to determine he location of

Figure 8. Variation of neutron reflectivity with time for ingress of dioctyl phthalate into a PMMA thin film.

Figure 10. Orientational ordering of lamellar fragments of DHTAC / C18E10 under elongation flow.

The Fig. 8 shows the evolution of the reflectivity profiles with time (measured at 20 second intervals) for the ingress of the plasticizer dioctyl phthalate into a PMMA thin film, where from the evolution of the film thickness with time the diffusion rate and mechanism can be determined. Access to kinetic data and the ultimate need for in-plane structural information is evident from the recent work of

the enzyme in its catalytic environment and follow the kinetics of the hydrolysis (Fig. 9). The processing of a variety of Soft Solids in many important industrial processes involves flow, from component mixing in pipe flow to extensional flow for the deliberate alignment by extrusion. To study the mechanisms controlling these processes at a molecular level requires access to realistic geometries and conditions,

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Figure 9. Model of interaction of PLA2 enzyme with DOPC membrane, derived from neutron reflectivity data (7).

RESEARCH INFRASTRUCTURES

and the ability to map the response to the complex spatial distributions of velocity and stress. Progress towards sub-millimeter spatial resolution and the use of complex flow geometries requires enhanced flux for small angle scattering, SANS. However, progress in this area is highlighted with two recent studies. Bent et al (8) demonstrated the use of SANS to spatially resolve the micro-structure of a polymer blend evolving in an extruder. The Fig. 10 shows the spatially resolved (resolution ~ 2mm) SANS data measured over the flow velocity pattern in a ‘crossed-slot’ geometry elongational flow cell for the mixed surfactant lamellar fragments of DHTAC / C18E10 (9). It illustrates a complex evolution of orientational ordering in response to the variation in the flow pattern Developing new drug encapsulation and delivery systems for the next generation of drugs with more specific targeting is a substantial challenge. In response a range of complex self-assembled and colloidal structures are being developed. These provide a ever increasing challenge for characterization and optimization. In particular the effective delivery of insoluble drug molecules is difficult. This is highlighted in a recent study by Barlow et al (10) on the solubilisation of steroid based drugs in oil-inwater microemulsions of DDAO / ethyl octanoate / wa-

sory Committee will consider proposals for the next phase of instrumentation, beyond that ‘day one’ suite. New and innovative designs and proposals are expected, and we can then start planning even more ambitious and complex studies.

References 1. J.R. Lu, R.K. Thomas, J. Penfold, Adv. Coll. Int. Sci., 84, 143 (2000). 2. J. Penfold, E. Staples, I. Tucker, R.K. Thomas, Langmuir, 20, 1269 (2004). 3. J. Penfold, E. Staples, I. Tucker, R.K. Thomas, Langmuir, 20, 2263 (2004). 4. A. Zarbakhsh, A. Querol, J. Bowers, J.R.P. Webster, Faraday Disc, 129, 155 (2005). 5. T.L. Kuhl, G.S. Smith, J.N. Isrealachivili, J. Majewski, W. Hamilton, Rev. Sci. Inst., 72, 1715 (2001). 6. J.S. Higgins, S.A. Butler, D.G. Bucknall, Macromol. Symp., 190, 1 (2002). 7. H.P. Vacklin, F. Tiberg, R.K. Thomas, Biophys. J., 84, 177A (2003). 8. J. Bent et al., Science, 301, 1691 (2003). 9. J. Penfold, I. Tucker et al, J. Phys. Chem. B., submitted (2005). 10. D.J. Barlow, M.J. Lawrence, T. Zuberi, S. Zuberi, R.K. Heenan, Langmuir, 16, 10398 (2000).

Figure 11. Schematic representation of the structure of a oil-in-water microemulsion.

ter. Here ‘contrast variation’ was used to investigate the microemulsion structure and the location of the solubilised drug (Fig. 11). While we eagerly await the new instruments which will become fully operational on TS-2 in 2008, the examples described above make the realization of what will be achievable to become increasingly evident. However, this is only the start, and in July 2005 the Scientific Advi-

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SR NEWS

LLB/Orphée THE FRENCH NEUTRON FACILITY

General Presentation of the Laboratoire Leon Brillouin The Laboratoire Léon Brillouin (LLB) is the French Neutron Facility, supported jointly by the Commissariat à l’Energie Atomique (CEA) and the Centre National de la Recherche Scientifique (CNRS). Both in-house and external scientific research programs in the field of condensed matter are carried out, using the neutron beams supplied by the O RPHÉE reactor. These programs cover a very large scientific range, from physics to chemistry, biology and material sciences. The LLB scientists closely collaborate with many groups, working predominantly for fundamental research, but also for applied research and industrial companies. The LLB “users” are from laboratories mainly located in France, but also in foreign countries, within the European Union and Eastern Europe. Applications for beam time at the LLB are submitted and selected twice a year via a Selection Panel procedure (deadlines for submission: April 1 st and October 1st). A description of the 23 LLB spectrometers is found at www-llb.cea.fr. Since 1992, the LLB is a regular partner of the European programs encouraging access to Large Installations. In the frame of the FP6 program, the LLB has been awarded an

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access-grant within the NMI3 consortium (NMI3: Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy), and is also implied in three NMI3-Joint Research Activities (MILAND, NO and PNT). LLB Scientific Higlights New electronic, magnetic and/or superconducting states in Condensed Matter Physics are the main “subjects” of LLB publications (Nature, Science, PRL, …) As for magnetic properties of materials under pressure, temperature and magnetic field, LLB is able to provide simultaneously 10GPa, 100mK and 8T, a world record. Two LLB diffractometers are now being upgraded: 3T2 [High-Resolution Powder Diffractometer / increase of the number of neutron counters] and G6.1 [HighPressure Powder Diffractometer, in order to be able to achieve measurements at pressures up to 100GPa]. LLB did play a key role in understanding the fundamental properties of Soft Matter. Today, our studies are dealing with new functionalised composite systems, like polymerspolyelectrolytes, polymers-proteins or grafted silica beads. In Biology, the objective is to determine the relationship between structure and dynamics in protein science, working on protein folding or localisation of

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water molecules in proteins. In this framework, a new “very small angle spectrometer (TPA)” is under construction, and will enable measurements on bigger size systems (>50nm). The technical study of a new quasi-elastic spectrometer “Fa#” is underway: with an improved counting rate of more than a factor 10, this TOF machine will enable completely new trends in the study of protein dynamics. Understanding the magnetic interaction between nano-objects on a surface is the challenge of the next few years. Thin layers magnetism is nearly present in every magnetic sensor, but not yet fully understood. The control of grafted polymers at the nanometre level is also a key point for the development of always smaller sensors. The new LLB time of flight reflectometer, EROS-2, will be soon able to measure layers of a thickness down to 0.5 nm. A LLB spectrometer, PAPYRUS, is dedicated to small angle surface scattering (GISANS), providing a wonderful tool for the study of functionalised surface nanomaterials. A clear future for the LLB: Summary of the last events Following an extensive debate on the role of neutrons for the development of science, the Minister of Research, Mr F. d’Aubert, decided in

M & N & SR NEWS

September 2004 to keep the French Neutron Facility Orphée-LLB operational. In October 2004, an extraordinary steering committee of the LLB consequently asked for a return to “normal” working conditions, namely 180 neutron days per year. In January 2005, the annual steering

committee of the LLB, approved these conditions for five years, starting on January 2006. At the same steering committee Dr Philippe Mangin, Professor at Nancy (Ecole des Mines, Institut National Polytechnique de Lorraine), has been nominated Director of the LLB, replacing Pierre Monceau, who is

now back at CRTBT (Grenoble). Michel Alba will remain as DeputyDirector until the end of 2005. The future of LLB is now clear. LLB will thus be able to reinforce the European scientific community, in the long term, jointly with the other European neutron sources. The LLB in the French and European Landscape Complementarities of the neutron and synchrotron radiation techniques are very well known and are or will be successfully applied either in Grenoble, Berlin, Hamburg, Villigen or Oxford. In 2006, SOLEIL, the new French synchrotron facility, will be in operation less than a kilometre away from the LLB, providing then to French and European scientists new combined working opportunities in Condensed Matter science. Françoise Bourée Laboratoire Léon Brillouin (CEA-CNRS) CEA/Saclay 91191 Gif-sur-Yvette CEDEX FRANCE

LLB and ORPHEE management in front of the ORPHEE reactor on October 4, 2004.

News from ESRF & ILL ESRF European science 'heavyweights' offer their help in the development of the knowledge-based economy Europe's seven major intergovernmental research organisations, working together in the EIROforum partnership, presented in April their comprehensive paper on science policy, "Towards a Europe of Knowledge and Innovation," in the presence of the European Commissioner for Science and Research, Mr. Janez Potoãnik and the Luxembourg Minister for Culture, Higher Education, Employment and Research, Mr.

François Biltgen. Luxembourg currently holds the presidency of the European Union. Five years ago, at the meeting of the European Council in Lisbon, the creation of a European Research Area (ERA) was proposed as a means to achieve the ambitious targets necessary to develop a leading, knowledge-based economy in Europe. The ERA intends to make a single market for European research, bringing together scientists from all member states. The EIROforum partners operate some of the largest research infrastructures in the world, possess unique and long-standing expertise

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in the organisation of pan-European research, bring expert knowledge to discussions about new large facilities in Europe, provide a model for the ERA, and offer their experience and active engagement in creating a true European Research Area. The EIROforum paper on science policy describes their collective vision on the future of European scientific research in order to support the Lisbon Process by working, alongside the Commission, for the implementation of the European Research Area. "As the borders of the European Union expand there is a fundamental role for the EIROforum part-

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M & N & SR NEWS

nership to work with the institutions of the European Union in the evolving environment," emphasizes JeanJacques Dordain, the Director General of ESA. ESA currently chairs EIROforum. The Paper presents many concrete ways in which EIROforum organisations can effectively participate in the consolidation of the ERA.

Attracting more young people is vital for the future of European research, and the EIROforum paper on science policy offers a series of actions to stimulate the interest of young people in science. It also subscribes to the European Commission strategy to recruit and retain world-leading scientists in Europe. This strategy should

Figure 2. The seven EIROforum organisations were represented by their directors at the launch of the Vision Paper.

ESRF Experiment Proposals Deadline: 1st September 2005 Submit your proposal online:

http://www.esrf.fr/Infrastructure/Computing/SMIS

ILL News from the Scientific Council The 72nd meeting of the Scientific Council was held for the last time under the Chairmanship of Prof. “Ted” Forgan (the man in the red shirt), who steps down as Chairman after long and very valuable service to the ILL Scientific Council. The meeting was largely devoted to the Review of ILL’s Instruments and to

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their future development. Overall, the subcommittees allocated 1254 days on all instruments (there were 50 days available for allocation this round). This represents 252 accepted proposals out of 439 submitted. News about CRGs The list of CRGs is as follows (status June 2005): operating: CRG-A: D1B, IN13

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be supported by a European Research Council (ERC) acting as an autonomous, science-driven agency endowed with sufficient funds to ensure European research is competitive at a global level. The EIROforum partners could also join European industry in technology platforms or large integrated projects that would enable the development of new scientific instrumentation, an area that needs European suppliers to secure and promote front-line research on our continent and generate important industrial spin-offs. EIROforum is a partnership created in 2002 between CERN, EFDA-JET, EMBL, ESA, ESO, ESRF and ILL, seven of Europe's major intergovernmental research organisations. The combined budget from the seven EIROforum Partners is comparable to that of the current Framework Programme of the European Union. Each of the organisations has become a world leader establishing a 'European Research Area' within its own field of science, thereby demonstrating the value and feasibility of pan-European collaboration in research. "The EIROforum organisations present visible proof that Europe and Europeans working together can achieve more than any individual national effort," asserts JeanJacques Dordain. Montserrat Capellas Espuny ESRF Press Officer

CRG-B: D15, D23, ADAM, IN12, IN22 CRG-C: S18, EVA Beam time for ILL use corresponds to 2.8 instruments under construction: CRG-B: Brillouin Spectrometer BRISP News from SCO Cancellation of the autumn 2005 proposal round

M & N & SR NEWS

As Table 1 indicates, after the 20052006 winter shutdown the reactor will not restart before June 2006. Therefore, we have decided to cancel the proposal deadline already planned in September 2005, because otherwise there will be 9-10 months delay between the submission of a proposal and the schedule of the allocated beam time. The subcommittee meetings planned in November 2005 will therefore also be cancelled. However, we will keep the Scientific Council as planned (temptative dates 6 - 7October 2005) and the Subcommittee Chairmen will be invited to attend as usual, to discuss scientific issues with the other members of the Scientific Council. We hope that this decision will not cause you too much trouble and we thank you in advance for your understanding. Next standard proposal round The deadline for proposal submission is Tuesday, 14 February 2006, 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 January 2006, and it will be closed on 14 February, 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 the Scientific Co-ordination Office: 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 Instruments available The following instruments will be available for the forthcoming round: • powder diffractometers: D1A, D1B*, D2B, D20, SALSA • 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 * Instruments marked with an asterisk are CRG instruments, where a smaller amount of beam time is available than on ILL-funded instru-

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ments, but we encourage such applications. You will find details of the instruments on the web: http://www.ill.fr/index_sc.html. Scheduling period Those proposals accepted at the next round, will be scheduled during the THREE CYCLES foreseen in 2006 (150 days). Reactor Cycles for 2006 Cycle n° 143 Cycle n° 144 Cycle n° 145

From

07/06/2006

27/07/2006

From

31/08/2006

20/10/2006

From

31/10/2006

20/12/2006

Table 1: The ILL reactor cycles in 2006. Startups and shut downs are planned at 8:30 am

Workshops The following workshops are planned by/at the ILL in the second half of 2005: • CONTENT (CONtinuous source Time-of-flight, Evolution, Novelties and Targets for future), ILL Grenoble , 30 June - 2 July 2005 • NSE2005 : Spin-Echo workshop at the ILL, September 8-10 2005 • Neutrons in Biology, a satellite meeting of the IUPAB/EBSA Biophysics Congress, ILL Grenoble 4-7 September 2005 For further information – as it becomes available – please refer to the ILL web-site: www.ill.fr, Events.

Giovanna Cicognani ILL Scientific Coordinator

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MEETING REPORTS

Second Italian-Australian Workshop on Future Directions in Spectroscopy and Imaging Trieste, 9th-11th February 2005 The first “Italian-Australian Workshop on Future Directions in Spectroscopy and Imaging” was held in Lorne, Australia in 2003, and on the basis of its success, the second edition was held in Trieste from the 9th to the 11 th of February, 2005. The venue for this meeting was the Abdus Salam International Centre for Theoretical Physics in Trieste, one of the best known centres for Physics in Europe. The ICTP also has beautiful views of the Adriatic coast and is next to the superb botanical gardens of Miramare castle. One speaker considered asking for the curtains of the conference room to be closed for fear that the view of Grignano bay might prove more interesting than his talk! The first major theme of the Workshop was imaging with synchrotron radiation. Theoretical analysis of hard x-ray imaging is a particular strength of the Australian community, especially with regard to phase retrieval techniques. Keith Nugent (Melbourne University) opened the conference by discussing methods for the recovery of structure from the diffraction patterns of non-periodic objects. This is an subject of crucial importance for fourth generation of synchrotron light sources, namely Free Electron X-ray Lasers. The determination of structure requires the recovery of phase, and this theme was continued by Andrew Peele (La Trobe University) and David Paganin (Monash University and CSIRO), who discussed experimental methods and numerical algorithms for image analysis. Lucia Mancini (Elettra) demonstrated the extensive range of technological problems solvable with phase contrast imaging, with many exam-

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ples from the SYRMEP beamline. The structure of objects as diverse as biological samples, archaeological artefacts and bread can be examined. For example, resins are used in the restoration of ancient glass, and the contrast between the two materials is poor with conventional, laboratory based x-ray techniques, based on absorption contrast. Using phase contrast and synchrotron light, good images can be obtained. Elettra has several world-class soft x-ray photoemission microscopes, and Luca Gregoratti (Elettra) is responsible for a scanning instrument at Elettra, the Escamicroscopy beamline, which is based on zone plates. The surfaces studied cover metals, semiconductors and heterogeneous catalytic surfaces. Stefan Heun (TASC-INFM) showed recent work from the Nanospectrocopy beamline and other work from the SPELEEM microscope. In this session, Burkhard Kaulich also described the newest microscope at Elettra, TwinMic, constructed in the framework of a European collaboration. It combines full field and scanning x-ray methods and is designed for in situ microscopy of a wide range of samples of practical and fundamental interest in biology, geochemistry, magnetism and environmental science. The wide energy range, from 250 to 3500 eV, makes this a versatile instrument. The next session was devoted to atomic and molecular spectroscpoy, a fertile field for innovation in instrumentation and experiments. Robert Richter (Elettra) described some demanding experiments, one of which was the measurement of photoabsorption by metastable helium atoms. A purpose built source

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was constructed to produce metastable helium atoms but the concentration was still very low. In addition a special detector was constructed and in spite of the difficulties this first measurement of its kind was successful. James Sullivan (ANU, Canberra) presented measurements on the lifetime of doubly excited states of helium, exploiting the time structure of a synchrotron in single bunch mode. The lifetimes of different fluorescent decay processes are different, so that a time dependent measurement separates them and gives the relative probability of each decay process. This is a clever example of how it is possible to measure the same physics in the time domain (by lifetime measurement) as is often done in the energy domain (using a wavelength dispersing spectrometer.) Finally Marcello Coreno (CNR) reviewed recent work on UV/visible fluorescence at the Gas Phase photoemission beamline at Elettra: helium, nitrogen and water were among the sample gases. For water excited at the oxygen K edge, fragmentation of the molecule occurs and fluorescence spectroscopy gives detailed information about these fragments. Robert Leckey (La Trobe University) continued the theme of spectroscopy. He showed beautiful Fermi surface maps of metals and discussed the problems of perpendicular momentum broadening, a process which is inherent in photoemission experiments from surfaces. Other fields covered were catalytic materials (Silvano Lizzit, Elettra), bio molecules on surfaces (Anton Stampfl, ANSTO, Sydney), amorphous semiconductors (Mark Ridgway, ANU), mineral science (Alan

MEETING REPORTS

Buckley, University of NSW, Sydney), organic thin film growth (Alberto Morgante, University of Trieste) and nitrogen based semiconductors (Milan Petravic, ANU). The last purely scientific session dealt the science that can be done with emerging techniques and methods. Steve Wilkins illustrated the planned medical imaging and therapy beamline at the Australian synchrotron, which will exploit the latest developments in phase contrast imaging. Claudio Masciovecchio (Elettra) showed the excellent results on liquids and glasses obtained recently at the Inelastic Ultraviolet Scattering beamline. For the Australian synchrotron, which is a higher energy machine, he suggested a hard x-ray inelastic scattering beamline would be very appropriate. Photoemission, a classical technique, is about to enter a new phase with the arrival of high energy (several keV), high resolution photoemission, as shown by Giancarlo Panaccione (INFM-TASC, Trieste). This will provide bulk sensitive spectra, and allow investigations of buried interfaces. Another bulk sensitive technique is Resonant Inelastic Soft Xray scattering, which has been largely enabled by the advent of third generation sources. Federica Bondi-

no (INFM-TASC) showed recent results from investigations of manganites, important materials for data storage technology. Bruce King (University of Newcastle, NSW) provided an intriguing glimpse of the future in experiments at the LEUTL Free Electron Laser at the APS. It was possible to perform ultra-trace analysis because a FEL pulse ionises most atoms or molecules in the gas phase that are in its path. Extremely small quantities of materials desorbed from surfaces can be mass analysed. Furthermore, organic samples undergo much less fragmentation with single photon ionization, in contrast to multi-photon laser ionization, so that the molecular mass of proteins can be accurately determined with a mass spectrometer. The workshop finished with a lively discussion of the technologies necessary to realise new experiments over the next few years. Industrial representatives of Jobin Yvon Italia, RMP and Cinel discussed the current state of the art in grating technology and precision mechanics in UHV. Daniele Cocco, Ralf Menk and Edoardo Busetto, all of Elettra, discussed aspects of x-ray optics and detection. Common themes emerged from a discussion that ranged widely over the needs of the community:

Giancarlo Panaccione explains the Volpe project.

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- thermal load management is still a problem, and better materials are needed for optical elements. - grating development is needed for energies from about 1 keV up to a few keV where crystal monochromators take over. The requirement is for both better resolving power and higher efficiency, and our industrial colleagues showed that this area is developing rapidly. - detector development is still behind light source development, for a variety of imaging and spectroscopic techniques. Robert Leckey reported problems of signal saturation with the toroidal analyser which his group had developed; a faster detector would improve things enormously. Steve Wilkins described the problems of real time imaging with hard x-rays, where the incident intensity was adequate, but the data could not be read fast enough. Ralf Menk mentioned the fact that in some hard xray experiments, more time is spent reading out the data than acquiring it. Keith Nugent commented that most experiments can still be done with existing technology; to stimulate development it is necessary to find an experiment which is impossible with existing technology. - a degree of standardization of beamline components would help to contain costs. The standards must be as flexible and as open as possible in order not to stifle innovation; but standardised specifications will help to avoid duplication. The workshop finished with enthusiastic support for the idea of a third Workshop, timed to coincide with the opening of the Australian synchrotron in the (Australian) Spring of 2007. Steve Wilkins was asked to coordinate the organization from the Australian side. We are sure that Australia will make a big contribution when it joins the international community of synchrotron light facility operators. K.C. Prince Elettra, Trieste, Italy

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SCIENTIFICREPORTS MEETING REVIEWS

Paper received May 2005

European Nanotechnology News Nanoquanta ETSF press release EURO NANOTECH NEWS 31st May 2005 EU funding to help establish European nanoscience facility The EU is to part-finance the creation of a European Theoretical Spectroscopy Facility (ETSF) along the lines of existing European synchrotron laboratories. The ETSF is an initiative put forward by the Nanoquanta Network of Excellence, funded under the nanotechnologies strand of the Sixth Framework Programme (FP6), with additional resources provided by national research funding organisations (from UK,

Germany, Belgium, Italy, France and Spain). The main objective of the ETSF will be to bring a deeper theoretical understanding of the science that underlies nanotechnologies to the wider scientific community. The ETSF will act as a professionally managed knowledge centre. At its core will be a number of collaborating research groups specialising in the theory of nanosciences or associated software developments, while users of the facility will be drawn from a much wider community, comprising

researchers from both the public and private sector that wish to benefit from the latest developments in the field. Such outreach initiatives will include the dissemination of theories, algorithms and computer programmes through publications, events and training sessions, as well as hosting visiting research teams from universities, research institutes and other organisations. The ETSF will also provide long-term training for users and doctoral students, as well as modules for Masters-level students. Further information on Nanoquanta web site: http://www.cmt.york.ac.uk/nanoquanta/Cordis fact sheet: http://ica.cordis.lu/search/?fuseaction=news.simpledocument&N_RC N=23887. R. Del Sole

Progress in Electron Volt Neutron Spectroscopy 24th April 2005, Santa Fe (New Mexico) US

A workshop on “Progress in Electron Volt Neutron Spectroscopy” was held on the Sunday (April 24th) at Santa Fe (New Mexico), preceding the ICANS-XVII meeting. The observational window provided by high-energy (many electron volt) neutrons offers unique possibilities for the exploration and understanding of condensed matter systems. This third editionsuch meeting (the first two took placed at RAL May 1995 and October 1998) has reviewed the progress of the field from its beginnings, discussed the most recent experiments measuring momentum distributions of light ions in a variety of systems, alternative means for doing the measurements, and the possibilities that the latest instrument developments provide for measuring

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www.fisica.uniroma2.it/~vesuvio/dins/index.html

the spectrum of electron volt excitations. A coherent set of topics brought together scientists to discuss of the state of art of momentum distributions and associated phenomena, an area of research which has benefited significantly from advances in high energy neutron spectroscopy. Jack Carpenter gave an introduction talk on the history of experimental technique, Jerry Mayers reviewed the instrumental aspects and capabilities of VESUVIO, the spectrometer which has pioneered Deep Inelastic Neutron Scattering measurements of the momentum distribution of light atoms in condensed matter systems. George Reiter reviewed a series of experiments on materials containing hydrogen, where the high energy neutrons probe the single proton dynamics measuring the proton wave function on a very short time scale and it is possible to distinguish between quantum tunnelling and thermally

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induced hopping of the proton between different sites. Roberto Senesi presented results of Deep Inelastic Neutron Scattering from dilute solutions of 3 He atoms in liquid 4 He, forming a prototype quantum liquid, as an example of an interacting boson-fermion mixture. Carla Andreani and Erik Schooneveld introduced the experimental and detector concepts of the novel experimental technique High energy Inelastic Neutron Scattering (HINS). Masatoshi Arai gave an account trial of eV Neutron Diffraction. As a whole the talks addressed the unique capabilities of the DINS technique as a local probe to detect spatial coherence and to make possible the reconstruction of local structure, as was well illustrated with the examples of KH2PO4, superprotonic conductors, bulk ice and water, water with acid and base solutes, water in nanotubes, 3He /4He mixtures. J. Mayers

MEETING REPORTS

Sweden joins ILL !! On the 4th April 2005, the Directors of the Swedish Research Council

and the Institute Laue-Langevin signed an agreement that welcomes

Sweden as the tenth member country of the ILL. This highly satisfactory outcome, effective from the 1st January 2005, is the first tangible result of an intense two-year programme to attract new European countries to ILL. The programme included such events as the New Partners Day held in June 2003, and the road shows held in Delft (Holland) and Krakow (Poland) in September 2004 where 11 countries were represented. We would like you to give a very warm welcome to those Swedish scientists who will soon come to ILL, having successfully gained access to 1.6% (27 experiment days) of the beam time on ILL instruments at the last Scientific Council. We look forward to a long and successful partnership between Sweden and ILL.

School on Pulsed Neutron Sources: Enhancing the Capacity for Material Science 17-28 October 2005, ICTP Trieste, Italy TOPICS - Design and Use of Neutron Sources - Layout and Optimization of Pulsed Spallation Sources - Data Processing and Analysis - Accelerator Generated Complementary Probes - Theory and Methodology of Materials Science with Neutrons - Selected Examples of Materials Science with Neutrons and Complementary Probes The aim of this School is to spread knowledge on the technology and application potential of neutron sources - in particular pulsed ones to materials science. While primarily focusing on materials research with neutrons, the complementary benefits offered by muons and syn-

chrotron radiation will be emphasized by short introductions to these techniques in the first week. Lectures on theoretical principles and examples of practical research topics will be the subject of the second half of the School. The School is designed to alert graduate and post-doctoral students to the possibilities offered by accelerator generated probes (neutrons, muons and synchrotron radiation) in the investigation of materials for practical applications and to familiarize them with the principles and technology of pulsed neutron sources and their application. It will cover all aspects of the design and optimization of pulsed neutron sources, explaining the flexibility

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and limitations that exist in providing customer-tailored beams for different kinds of applications. The idea is to bring together potential future source designers and users, establish contacts and generate a better mutual understanding on the one hand and to encourage the use of existing facilities on the other. To apply for this activity, please contact smr1678@ictp.it before 30 June 2005. School on Pulsed Neutron Sources smr1678@ictp.it c/o Ms. Suzie Radosic the Abdus Salam International Centre for Theoretical Physics Strada Costiera 11 34014 Trieste - Italy

NOTIZIARIO NEUTRONI E LUCE DI SINCROTRONE

CALENDAR

July 4 - 7, 2005

GRENOBLE, FRANCE

I7th International Workshop on Radiation Imaging Detectors (IWORID-7) ESRF http://www.esrf.fr/Conferences/IWORID7/

July 7 - 9, 2005

ZUOZ, SWITZERLAND

Aug 6 - 13, 2005

OXFORD, UK

International Conference on Muon Spin Rotation, Relaxation and Resonance Oxford, UK http://musr05.physics.ox.ac.uk/

NEW LONDON, NH, USA

Gordon Research Conference on X-ray Physics 2005 Colby-Sawyer College, New London, NH (USA) http://www.grc.org/programs/2005/xray.htm

Aug 14 - 17, 2005

BLOOMINGTON, IN, USA

Workshop on "Probing complex fluid membranes and films with neutron spin-echo" Indiana University, Bloomington, IN, USA Email:moywrigh@indiana.edu http://www.iucf.indiana.edu/events/neutronmembrane/

NOTIZIARIO NEUTRONI E LUCE DI SINCROTRONE

4th PSI Summer School on Condensed Matter Research: Spectroscopy / Microscopy Lyceum Alpinum, Zuoz, Switzerland Email: christine.kunz@psi.ch http://sls.web.psi.ch/zuoz2005

Aug 14 - 28, 2005

4th PSI Summer School on Condensed Matter Research Lyceum Alpinum, Zuoz, Switzerland http://sls.web.psi.ch/view.php/science/events/Conferences/Zuoz2005/Scope.html

Aug 7 - 12, 2005

ZUOZ, SWITZERLAND

MODENA, ITALY

13th SILS Conference http://www.s3.infm.it/SILS/index.php

Aug 4 - 21, 2005

Aug 14 - 21, 2005

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ILLINOIS, USA

National School of Neutron and X-ray Scattering Argonne National Laboratory, Illinois, USA Email: nxschool@dep.anl.gov http://www.dep.anl.gov/nx/

Sep 1 - 2, 2005

EDINBURGH, UK

Neutron Scattering Group Meeting: Magnetism, Neutrons and High-Pressure Centre for Science at Extreme Conditions (CSEC), University of Edinburgh, United Kingdom http://www.csec.ed.ac.uk/NSG_main.html

Sep 4 - 7, 2005

GRENOBLE, FRANCE

Neutrons in Biology - Satellite meeting of the IUPAB/EBSA World Biophysics Congress Montpellier, Institut Laue-Langevin, Grenoble, France http://whisky.ill.fr/neutbio2005/frameset_accueil.html

Sep 5 - 15, 2005

OXFORD, UK

9th Oxford School on Neutron Scattering University of Oxford, U.K. http://www.isis.rl.ac.uk/conferences/osns2005/

Sep 7 - 10, 2005

GRENOBLE, FRANCE

The NSE2005 workshop Contact: Institut Laue-Langevin, 6 rue Jules Horowitz, B.P. 156, F-38042 Grenoble Cedex, France Fax: +33 (0)4.76.20.76.88 http://www.ill.fr/YellowBook/IN11/NSE2005/

CALENDAR

Sep 12 - 23, 2005

JULICH, GERMANY

9th Laboratory Course for Neutron Scattering Juelich, Germany Email: R.Zorn@fz-juelich.de http://www.fz-juelich.de/iff/wns_lab05

Sep 25 - 30, 2005

COLUMBIA, SC, USA

Theoretical Problems in Fundamental Neutron Physics Columbia, SC, USA Email: papp@physics.sc.edu http://www.physics.sc.edu/TPFNP/

Oct 17 - 28, 2005

TRIESTE, ITALY

School on Pulsed Neutron Sources: Enhancing the Capacity for Material Science Miramare - Trieste, Italy http://users.ictp.trieste.it/~smr1678/

Nov 27 - Dec 2, 2005

13th International Conference on Small-Angle Scattering (SAS2006 Kyoto) Kyoto, Japan Email: SAS2006@alloy.polym.kyoto-u.ac.jp http://sas2006.scphys.kyoto-u.ac.jp/

Sep 25 - 28, 2006

BERLIN. GERMANY

Polarised Neutrons in Condensed Matter Investigations (PNCMI 2006) http://www.hmi.de/bensc/pncmi2006/

GRENOBLE, FRANCE

Workshop on Reflectometry, Off-specular Scattering and GISANS Institut Laue Langevin, Grenoble, France http://neutron.neutron-eu.net/n_news/n_calendar_ of_events/n-events-2005/694

Oct 14 - 15, 2005

BERLIN. GERMANY

ROME, ITALY

18th International Conference on X-ray Optics Microanalysis Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare; Via Fermi 40, Frascati, Roma, Italy E-mail: icxom05@lnf.infn.it http://www.lnf.infn.it/conference/2005/icxom

October, 2005

July 9 - 13, 2006

SYDNEY, AUSTRALIA

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

The PhD curriculum in Nanostructures and Nanotechnology at the University of Milano Bicocca takes three years and allows students to interact with several European institutions, in order to produce an original thesis work and complete training in nonosciente. Available projects in the laboratories of the University of Milano Bicocca and the ones of partner institutions, such as the University of Rome Tor Vergata and the Politecnic School of Milano at Como, include synthesis, characterization and modeling of nanostructured polymeric materials, carbon nanotubes, semiconductor quantum dots and epitaxial films, nanocrystalline materials, organic epitaxial films, oxide nanoclusters, supramolecular systems, microcavities. The mission of the PhD curriculum is to educate material scientists, physicists, chemists and engineers in the interdisciplinary area of nanoscience and nanotechnology for research positions in public and industrial research laboratories. More information and indications how to apply for a position can be obtained at the web site www.nano.unimib.it or contacting the director at leo.miglio@unimib.it, before July 15, 2005. Leo Miglio

Vol. 10 n. 2 July 2005

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NOTIZIARIO NEUTRONI E LUCE DI SINCROTRONE

CALL FOR PROPOSAL

Call for proposals for

Neutron Sources

Synchrotron Radiation Sources

BENSC

ALS

Deadlines for proposal submission are: 15 September 2005 and 15 March 2006

Deadlines for proposal submission are: 15 March and 1 June 2005

BNC

BESSY

Deadlines for proposal submission is: 15 November 2005 and 15 June 2006

Deadlines for proposal submission are: 4 August 2005 and 15 February 2006

FZ Juelich

DARESBURY

Deadline for proposal submission is: 1 February 2006

Deadlines for proposal submission are: 31 October 2005 and 30 April 2006

GeNF

ELETTRA

Deadline for proposal submission is: Anytime during 2005

Deadlines for proposal submission are: 31 August 2005 and 28 February 2006

ILL

ESRF

Deadline for proposal submission is: 15 February 2006

Deadlines for proposal submission are: 1 September 2005 and 1 March 2006

ISIS

GILDA

Deadlines for proposal submission are: 16 October 2005 and 16 April 2006

Deadlines for proposal submission are: 1 November 2005 and 1 May 2006

LLB-ORPHEE-SACLAY

HASYLAB

Deadline for proposal submission is: 1 October 2005

Deadlines for proposal submission are: 1 september, 1 december 2005 and 1 march 2006

NFL

LURE

Deadlines for proposal submission is: 15 September 2005, 15 January and 15 May 2006

Deadline for proposal submission is: 30 october 2005

NPI-Rez

MAX-LAB

Deadline for proposal submission is: 1 January 2006

Deadline for proposal submission is: february 2006

SINQ

NSLS

Deadlines for proposal submission are: 15 November 2005 and 15 May 2006

Deadlines for proposal submission are: 30 September 2005, 31 January and 31 May 2006

NOTIZIARIO NEUTRONI E LUCE DI SINCROTRONE

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Vol. 10 n. 2 July 2005

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/ 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 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 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 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 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/ 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/

CLS Canadian Light Source, University of Saskatchewan, 101 Perimeter Road, Saskatoon, SK., Canada. S7N 0X4 http://www.cls.usask.ca/ 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/ DELTA Universität Dortmund,Emil Figge Str 74b, 44221 Dortmund, Germany tel: +49 231 7555383 - fax: +49 231 7555398 http://prian.physik.uni-dortmund.de/ DIAMOND Diamond Light Source Ltd, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX http://www.diamond.ac.uk/ ELETTRA Sincrotrone Trieste S.C.p.A., Strada Statale 14 - Km 163,5 in AREA Science Park, 34012 Basovizza, Trieste, Italy tel: +39 40 37581 - fax: +39 40 226338 http://www.elettra.trieste.it 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 ESRF European Synchrotron Radiation Lab. BP 220, F-38043 Grenoble, France tel: +33 476 882000 - fax: +33 476 882020 http://www.esrf.fr/ EUTERPE Cyclotron Lab.,Eindhoven Univ. of Technol, P.O.Box 513, 5600 MB Eindhoven, The Netherlands tel: +31 40 474048 - fax: +31 40 438060 HASYLAB Notkestrasse 85, D-2000, Hamburg 52, Germany tel: +49 40 89982304 - fax: +49 40 89982787 http://www-hasylab.desy.de/

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FACILITIES

INDUS Center for Advanced Technology, Rajendra Nagar, Indore 452012, India tel: +91 731 64626 http://www.ee.ualberta.ca/~naik/accind1.html 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/ Kurchatov Kurchatov Inst. of Atomic Energy, SR Center, Kurchatov Square, Moscow 123182, Russia tel: +7 95 1964546 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/ LURE Bât 209-D, 91405 Orsay ,France tel: +33 1 64468014 - fax: +33 1 64464148 http://www.lure.u-psud.fr MAX-Lab Box 118, University of Lund, S-22100 Lund, Sweden tel: +46 46 109697 - fax: +46 46 104710 http://www.maxlab.lu.se/ 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/ 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 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 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 SLS Swiss Light Source Paul Scherrer Institut, User Office, CH-5232 Villigen PSI,

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Switzerland tel: +41 56 310 4666 - fax: +41 56 310 3294 E-mail slsuo@psi.ch - http://sls.web.psi.ch 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 SOLEIL Centre Universitaire - B.P. 34 - 91898 Orsay Cedex http://www.soleil.u-psud.fr/ 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 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 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/ 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 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 SURF III B119, NIST, Gaithersburg, MD 20859, USA tel: +1 301 9753726 - fax: +1 301 8697628 http://physics.nist.gov/MajResFac/surf/surf.html TERAS ElectroTechnical Lab. 1-1-4 Umezono, Tsukuba Ibaraki 305, Japan tel: 81 298 54 5541 - fax: 81 298 55 6608 UVSOR Inst. for Molecular ScienceMyodaiji, Okazaki 444, Japan tel: +81 564 526101 - fax: +81 564 547079

FACILITIES

NEUTRONI NEUTRON SCATTERING WWW SERVERS IN THE WORLD (http://neutron.neutron-eu.net/n_news/n_calendar_of_events) 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 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.nrc-cnrc.gc.ca/home.html 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 FRJ-2 Research Reactor in Jüelich (D) Type: Dido reactor. Flux: 2 x 1014 n/cm2/s Prof. D. Richter, Forschungszentrums Jüelich GmbH, Institut für Festkörperforschung, Postfach 19 13, 52425 Jüelich, Germany Tel: +49 2461161 2499; Fax: +49 2461161 2610 E-mail: neutron@fz-juelich.de http://www.neutronscattering.de 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. Wfn-Neutronscattering, 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

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-Meitner-Insitut, 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 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 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 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 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

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FACILITIES

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

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 E-mail: mike.rowe@nist.gov http://www.ncnr.nist.gov/

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/

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

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

PSI-SINQ Villigen (CH) Type: Steady spallation source. Flux: 2.0 x 1014 n/cm2/s Contact address: Paul Scherrer Institut User Office, CH-5232 Villigen PSI - Switzerland Tel: +41 56 310 4666; Fax: +41 56 310 3294 E-mail: sinq@psi.ch; http://sinq.web.psi.ch

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

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

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

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