Lasercenter VU Amsterdam

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How to reach Laser Centre Vrije Universiteit?

• from Schiphol Airport: train to Amsterdam Zuid/World Trade Centre (5 min), transfer to tram line 5, or metro line 51, direction Amstelveen, first stop is VU/De Boelelaan.

• from Amsterdam Central Station: tram line 5 or metro line 51, direction Amstelveen, exit at VU/ De Boelelaan.

• by car: city ring A10 (zuid), exit S108 Amstelveen, turn south, turn left after about 200 meter to VU hospital on the De Boelelaan, the University Campus is next to the hospital.

Laser Centre VU Amsterdam

De B oele laan

Prof. Dr. W. Hogervorst (director) Atomic and Laser Physics Tel: 31-20-444 79 47 e-mail: wh@nat.vu.nl

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Prof. Dr. S. Stolte Physical Chemistry Tel: 31-20-444 76 33 e-mail: stolte@chem.vu.nl Prof. Dr. D. Lenstra Quantum Optics Theory Tel: 31-20-444 78 55 e-mail: lenstra@nat.vu.nl Prof. Dr. R. van Grondelle Biophysics Tel: 31-20-444 79 30 e-mail: rienk@nat.vu.nl

The Laser Centre Vrije Universiteit Amsterdam (LCVU) is a multi-disciplinary facility in which physicists, chemists and biologists have combined their laser-oriented research activities. They share a common infrastructure of an exceptionally well-equipped laboratory with state-of-the-art laser systems, auxiliary equipment and computer facilities. A multitude of pulsed and CW laser systems in the infrared, visible, ultraviolet is available as well as a

Prof. Dr. C. Gooijer Analytical Chemistry Tel: 31-20-444 75 40 e-mail: gooijer@chem.vu.nl

facility for the generation of extreme ultraviolet radiation. Research activities, performed in a large number of relatively small-scale experiments, vary from fundamental studies of atoms and molecules, laser cooling and manipulation of atoms, dynamics of photosynthesis, chemical reaction dynamics and fluorescence spectroscopy of

Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1081-1083, 1081 HV Amsterdam NL

bio-molecules to more applied studies of environmental trace analysis and atmospheric, bio-analytical and photochemical chemistry. This makes LCVU an excellent place for visiting scientists from various disciplines.

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0002054/LaserBrchr/DEFINITIEF

06-05-2002

16:24

Pagina 3

How to reach Laser Centre Vrije Universiteit?

• from Schiphol Airport: train to Amsterdam Zuid/World Trade Centre (5 min), transfer to tram line 5, or metro line 51, direction Amstelveen, first stop is VU/De Boelelaan.

• from Amsterdam Central Station: tram line 5 or metro line 51, direction Amstelveen, exit at VU/ De Boelelaan.

• by car: city ring A10 (zuid), exit S108 Amstelveen, turn south, turn left after about 200 meter to VU hospital on the De Boelelaan, the University Campus is next to the hospital.

Laser Centre VU Amsterdam

De B oele laan

Prof. Dr. W. Hogervorst (director) Atomic and Laser Physics Tel: 31-20-444 79 47 e-mail: wh@nat.vu.nl

l a s e r

c e n t r e

v u

a m s t e r d a m

Prof. Dr. S. Stolte Physical Chemistry Tel: 31-20-444 76 33 e-mail: stolte@chem.vu.nl Prof. Dr. D. Lenstra Quantum Optics Theory Tel: 31-20-444 78 55 e-mail: lenstra@nat.vu.nl Prof. Dr. R. van Grondelle Biophysics Tel: 31-20-444 79 30 e-mail: rienk@nat.vu.nl

The Laser Centre Vrije Universiteit Amsterdam (LCVU) is a multi-disciplinary facility in which physicists, chemists and biologists have combined their laser-oriented research activities. They share a common infrastructure of an exceptionally well-equipped laboratory with state-of-the-art laser systems, auxiliary equipment and computer facilities. A multitude of pulsed and CW laser systems in the infrared, visible, ultraviolet is available as well as a

Prof. Dr. C. Gooijer Analytical Chemistry Tel: 31-20-444 75 40 e-mail: gooijer@chem.vu.nl

facility for the generation of extreme ultraviolet radiation. Research activities, performed in a large number of relatively small-scale experiments, vary from fundamental studies of atoms and molecules, laser cooling and manipulation of atoms, dynamics of photosynthesis, chemical reaction dynamics and fluorescence spectroscopy of

Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1081-1083, 1081 HV Amsterdam NL

bio-molecules to more applied studies of environmental trace analysis and atmospheric, bio-analytical and photochemical chemistry. This makes LCVU an excellent place for visiting scientists from various disciplines.

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06-05-2002

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Atomic and Laser Physics

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Research is concerned with the interaction of laser light with atoms and molecules. This interaction can be used to cool metastable helium atoms to ultra-low temperatures. With powerful lasers radiation at short wavelength is generated using non-linear optical processes. The energetic photons are used to investigate atoms and small

3-5 Large numbers of laser-cooled metastable helium atoms can be stored in magneto-optical and magnetostatic traps. With the isotope 4He options to create a macroscopic quantum state of matter (Bose-Einstein condensate) are being explored. Further experiments involve the realisation of an accurate atomic clock based on laser-cooled 3He atoms, and new approaches to build nano-scale structures with atom lithography.

molecules such as H2 and CO. Applied atomic and molecular spectroscopy and laser development are also part of the group’s activities.

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Doppler-free, high resolution spectroscopy is performed on beams of rare-earth atoms. Rydberg and autoionising states are populated in multi-step excitation processes using pulsed or CW laser systems.

Short-wavelength laser radiation can be generated by focussing powerful, pulsed visible laser light in a gaseous medium. Through a non-linear optical process higher harmonics of the fundamental radiation are produced. A bright source of narrowband coherent radiation for high resolution spectroscopy of atoms and molecules in the wavelength range 50-200 nm is operational; extension to 20 nm is pursued. With this source some surprising new data on highly-excited, exotic states of the H2 molecule have been obtained.

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0002054/LaserBrchr/DEFINITIEF

06-05-2002

12:21

Pagina 6

Atomic and Laser Physics

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Research is concerned with the interaction of laser light with atoms and molecules. This interaction can be used to cool metastable helium atoms to ultra-low temperatures. With powerful lasers radiation at short wavelength is generated using non-linear optical processes. The energetic photons are used to investigate atoms and small

3-5 Large numbers of laser-cooled metastable helium atoms can be stored in magneto-optical and magnetostatic traps. With the isotope 4He options to create a macroscopic quantum state of matter (Bose-Einstein condensate) are being explored. Further experiments involve the realisation of an accurate atomic clock based on laser-cooled 3He atoms, and new approaches to build nano-scale structures with atom lithography.

molecules such as H2 and CO. Applied atomic and molecular spectroscopy and laser development are also part of the group’s activities.

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2

4

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2

Doppler-free, high resolution spectroscopy is performed on beams of rare-earth atoms. Rydberg and autoionising states are populated in multi-step excitation processes using pulsed or CW laser systems.

Short-wavelength laser radiation can be generated by focussing powerful, pulsed visible laser light in a gaseous medium. Through a non-linear optical process higher harmonics of the fundamental radiation are produced. A bright source of narrowband coherent radiation for high resolution spectroscopy of atoms and molecules in the wavelength range 50-200 nm is operational; extension to 20 nm is pursued. With this source some surprising new data on highly-excited, exotic states of the H2 molecule have been obtained.

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0002054/LaserBrchr/DEFINITIEF

06-05-2002

12:49

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Physical Chemistry

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Research activities are mainly oriented towards a fundamental study of reactivity and energy transfer in chemical dynamics. Processes of interest to atmospheric chemistry and surface science are studied at the state-to-state quantum level of both reactants and products.

A broad range of femtosecond, nanosecond and continuous single-frequency laser systems is applied in combination with molecular beam techniques to study and control chemical dynamics.

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A cylindrical hexapole serves as a focusing quantum state selector for polar molecules by virtue of its high electric field gradients.

The selected molecules can then be oriented with a uniform electric field to study the effect of orientation on the outcome of a collision with other molecules or atoms, or on photolysis.

Angular and velocity resolved recoil of fragments resulting from laser photolysis of isotropic and oriented CX 3Y reactant molecules, such as CH3I.

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A diode laser is externally injected with a time-reversed feedback induced by phaseconjugated reflection in a Rb vapour. At a feedback level of only 10-3 a chaotic coherence collapse is observed in the output of the diode. The application of this type of feedback to achieve GHz rate encrypted optical communication is investigated now.

This experimental study is carried out in close collaboration with the theoretical quantum optics group.

Laser spectroscopy can elucidate highlyexcited molecular states on multiple electronic surfaces. A conical intersection between two potential surfaces may result in a breakdown of the Born-Oppenheimer approximation. The structure of the hyperfine-resolved excitation spectrum reveals the resulting electronically mixed character of the NO2 eigenstates.

0002054/LaserBrchr/DEFINITIEF

06-05-2002

12:49

Pagina 8

Physical Chemistry

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Research activities are mainly oriented towards a fundamental study of reactivity and energy transfer in chemical dynamics. Processes of interest to atmospheric chemistry and surface science are studied at the state-to-state quantum level of both reactants and products.

A broad range of femtosecond, nanosecond and continuous single-frequency laser systems is applied in combination with molecular beam techniques to study and control chemical dynamics.

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A cylindrical hexapole serves as a focusing quantum state selector for polar molecules by virtue of its high electric field gradients.

The selected molecules can then be oriented with a uniform electric field to study the effect of orientation on the outcome of a collision with other molecules or atoms, or on photolysis.

Angular and velocity resolved recoil of fragments resulting from laser photolysis of isotropic and oriented CX 3Y reactant molecules, such as CH3I.

4

A diode laser is externally injected with a time-reversed feedback induced by phaseconjugated reflection in a Rb vapour. At a feedback level of only 10-3 a chaotic coherence collapse is observed in the output of the diode. The application of this type of feedback to achieve GHz rate encrypted optical communication is investigated now.

This experimental study is carried out in close collaboration with the theoretical quantum optics group.

Laser spectroscopy can elucidate highlyexcited molecular states on multiple electronic surfaces. A conical intersection between two potential surfaces may result in a breakdown of the Born-Oppenheimer approximation. The structure of the hyperfine-resolved excitation spectrum reveals the resulting electronically mixed character of the NO2 eigenstates.

0002054/LaserBrchr/DEFINITIEF

06-05-2002

13:50

Pagina 10

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Photosynthesis takes place in membranes of chloroplasts. An electron microscopic image of a paired photosynthetic membrane is shown, in which several pigment-protein complexes can be observed.

Detailed electron-microscope image of a photosynthetic pigmentprotein complex. This complex (called photosystem 2) binds about 400 chlorophyll molecules that absorb light, transfer excitation energy and induce a charge separation across the membrane on the time scale of about one picosecond.

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Biophysics 4

Research in the Biophysics group is aimed at resolving basic (bio)physical concepts of photosynthesis, the process by which green plants and algae efficiently convert light into chemical free energy. It is focused in particular on the 5

analysis of the first, extremely fast processes, which are studied using ultra-fast laser spectroscopy, รกnd on the relation between these fundamental processes and the molecular structure and biological function.

A synchroscan streak camera combined with a spectrograph monitors spectral and temporal fluorescence changes of photosynthetic pigment-protein complexes with about one picosecond time resolution. Ultrafast absorption difference changes can be detected using the technique of pump-probe spectroscopy.

Fluorescence intensity as a function of time (vertical) and wavelength (horizontal) of a photosystem 1 preparation after excitation by an ultrashort laser pulse. This image, which covers a 200 ps time window and a 315 nm spectral window, is obtained with a streak camera. Different colours represent different intensities.

Ultrafast spectroscopic measurements such as those obtained with a streak camera are processed by global analysis. The so-called decay-associated spectra shown reveal the dynamics of the migration of the excited electronic states through the complex.

0002054/LaserBrchr/DEFINITIEF

06-05-2002

13:50

Pagina 10

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Photosynthesis takes place in membranes of chloroplasts. An electron microscopic image of a paired photosynthetic membrane is shown, in which several pigment-protein complexes can be observed.

Detailed electron-microscope image of a photosynthetic pigmentprotein complex. This complex (called photosystem 2) binds about 400 chlorophyll molecules that absorb light, transfer excitation energy and induce a charge separation across the membrane on the time scale of about one picosecond.

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Biophysics 4

Research in the Biophysics group is aimed at resolving basic (bio)physical concepts of photosynthesis, the process by which green plants and algae efficiently convert light into chemical free energy. It is focused in particular on the 5

analysis of the first, extremely fast processes, which are studied using ultra-fast laser spectroscopy, รกnd on the relation between these fundamental processes and the molecular structure and biological function.

A synchroscan streak camera combined with a spectrograph monitors spectral and temporal fluorescence changes of photosynthetic pigment-protein complexes with about one picosecond time resolution. Ultrafast absorption difference changes can be detected using the technique of pump-probe spectroscopy.

Fluorescence intensity as a function of time (vertical) and wavelength (horizontal) of a photosystem 1 preparation after excitation by an ultrashort laser pulse. This image, which covers a 200 ps time window and a 315 nm spectral window, is obtained with a streak camera. Different colours represent different intensities.

Ultrafast spectroscopic measurements such as those obtained with a streak camera are processed by global analysis. The so-called decay-associated spectra shown reveal the dynamics of the migration of the excited electronic states through the complex.

0002054/LaserBrchr/DEFINITIEF

06-05-2002

15:52

Pagina 12

Applied Laser Spectroscopy

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Research is directed towards the development of molecular laser spectroscopic detection and identification methods (Raman, fluorescence), coupled on-line to advanced separation techniques, to solve challenging environmental problems and to study the interaction of small molecules with biopolymeric systems. Physical

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chemistry of complex molecular systems is also a topic of fundamental research interest.

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A challenging environmental problem is the elucidation of the biodegradation routes of toxic compounds like polycyclic aromatic hydrocarbons (PAHs) and their interaction with DNA or proteins in living organisms. Special modes of fluorescence spectroscopy, e.g. fluorescence line-narrowing (a cryogenic laser technique that provides detailed vibrational patterns) can be used to identify PAH metabolites directly in small animals like isopods (Porcellio scaber).

Raman spectroscopy is an analytical technique that can provide detailed vibrational information for “fingerprint� identification. It is applicable to aqueous samples, such as bioanalytical systems. The on-line combination of Raman spectroscopy with high-performance separation techniques such as column liquid chromatography is hampered by low sensitivity. This limitation can be overcome with detector cells with an extremely long optical path length. Such cells are based on liquid-core waveguides composed of plastic materials with a refractive index lower than that of water, thus giving total internal reflection.

Interfaces are being developed to couple spectroscopic identification techniques to liquid chromatography (LC). Fluorescence line-narrowing spectroscopy is performed at cryogenic temperatures (typically 10 K). Surface-enhanced resonance Raman spectroscopy requires the addition of silver sol. Fourier-transform infrared spectroscopy requires removal of the aqueous phase. In the atline approach the chromatogram is deposited on a moving substrate, without loss of chromatographic resolution, while the LC effluent is evaporated by means of a spray jet assembly. The separated spots can then be analysed using the spectroscopic technique of choice.

Proteins, like cytochrome c, are prime examples of complex physico-chemical systems. The oxidation states of the iron (grey) at the centre of the heme (red) are stabilized by subtle changes in the position of the histidine (yellow) side chain. The function and properties are to a large extent determined by the secondary (alpha helix) and the tertiary (folded) structure, which is shaped by genetic, and ultimately evolutionary forces. A variety of linear and nonlinear optical techniques are used to study the structure and dynamics of these systems. Emphasis is on temperature jump techniques to induce unfolding and refolding of the protein, resonance Raman to study heme binding, and fluorescence energy transfer to obtain information on intra- and intermolucular distances.

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0002054/LaserBrchr/DEFINITIEF

06-05-2002

15:52

Pagina 12

Applied Laser Spectroscopy

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Research is directed towards the development of molecular laser spectroscopic detection and identification methods (Raman, fluorescence), coupled on-line to advanced separation techniques, to solve challenging environmental problems and to study the interaction of small molecules with biopolymeric systems. Physical

4

chemistry of complex molecular systems is also a topic of fundamental research interest.

1

2

10

1

2

A challenging environmental problem is the elucidation of the biodegradation routes of toxic compounds like polycyclic aromatic hydrocarbons (PAHs) and their interaction with DNA or proteins in living organisms. Special modes of fluorescence spectroscopy, e.g. fluorescence line-narrowing (a cryogenic laser technique that provides detailed vibrational patterns) can be used to identify PAH metabolites directly in small animals like isopods (Porcellio scaber).

Raman spectroscopy is an analytical technique that can provide detailed vibrational information for “fingerprint� identification. It is applicable to aqueous samples, such as bioanalytical systems. The on-line combination of Raman spectroscopy with high-performance separation techniques such as column liquid chromatography is hampered by low sensitivity. This limitation can be overcome with detector cells with an extremely long optical path length. Such cells are based on liquid-core waveguides composed of plastic materials with a refractive index lower than that of water, thus giving total internal reflection.

Interfaces are being developed to couple spectroscopic identification techniques to liquid chromatography (LC). Fluorescence line-narrowing spectroscopy is performed at cryogenic temperatures (typically 10 K). Surface-enhanced resonance Raman spectroscopy requires the addition of silver sol. Fourier-transform infrared spectroscopy requires removal of the aqueous phase. In the atline approach the chromatogram is deposited on a moving substrate, without loss of chromatographic resolution, while the LC effluent is evaporated by means of a spray jet assembly. The separated spots can then be analysed using the spectroscopic technique of choice.

Proteins, like cytochrome c, are prime examples of complex physico-chemical systems. The oxidation states of the iron (grey) at the centre of the heme (red) are stabilized by subtle changes in the position of the histidine (yellow) side chain. The function and properties are to a large extent determined by the secondary (alpha helix) and the tertiary (folded) structure, which is shaped by genetic, and ultimately evolutionary forces. A variety of linear and nonlinear optical techniques are used to study the structure and dynamics of these systems. Emphasis is on temperature jump techniques to induce unfolding and refolding of the protein, resonance Raman to study heme binding, and fluorescence energy transfer to obtain information on intra- and intermolucular distances.

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0002054/LaserBrchr/DEFINITIEF

06-05-2002

16:15

Pagina 14

Laser Centre Vrije Universiteit Faculty of Sciences De Boelelaan 1081-1083, 1081HV Amsterdam The Netherlands +31-20-444 78 90 (secretary) +31-20-444 79 99 (FAX) Internet: http://www.nat.vu.nl/~laser/ http://www.chem.vu.nl e-mail: gijp@nat.vu.nl Production STAP TK&O, Amsterdam: Pieter Kers and Ron Bergman, photography Jean Trienes, design Print: Drukkerij Mart Spruijt BV, Amsterdam