A5000707265- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Magnetism in coordination complexes
- Advanced X-ray Imaging Techniques
- Metal-Catalyzed Oxygenation Mechanisms
- Photochemistry and Electron Transfer Studies
- Electron and X-Ray Spectroscopy Techniques
- Electron Spin Resonance Studies
- Lanthanide and Transition Metal Complexes
- Metal complexes synthesis and properties
- Laser-Matter Interactions and Applications
- Mass Spectrometry Techniques and Applications
- Advanced Electron Microscopy Techniques and Applications
- Spectroscopy and Laser Applications
- Photosynthetic Processes and Mechanisms
- Atmospheric Ozone and Climate
- Nuclear Physics and Applications
- Atomic and Molecular Physics
- CO2 Reduction Techniques and Catalysts
- Particle Accelerators and Free-Electron Lasers
- nanoparticles nucleation surface interactions
- Porphyrin and Phthalocyanine Chemistry
- Various Chemistry Research Topics
- Diamond and Carbon-based Materials Research
Hamburg Centre for Ultrafast Imaging
2015-2024
European X-Ray Free-Electron Laser
2015-2024
Universität Hamburg
2014-2024
Max Planck Institute for the Structure and Dynamics of Matter
2015-2024
Technical University of Denmark
2012-2023
École Polytechnique Fédérale de Lausanne
2004-2012
Deutsches Elektronen-Synchrotron DESY
2009-2010
Paul Scherrer Institute
1998-2009
Swiss Light Source
2006-2009
Lawrence Berkeley National Laboratory
2008
X-ray absorption spectroscopy is a powerful probe of molecular structure, but it has previously been too slow to track the earliest dynamics after photoexcitation. We investigated ultrafast formation lowest quintet state aqueous iron(II) tris(bipyridine) upon excitation singlet metal-to-ligand-charge-transfer (1MLCT) by femtosecond optical pump/x-ray techniques based on x-ray near-edge structure (XANES). By recording intensity characteristic XANES feature as function laser time delay, we...
The ultrafast relaxation of aqueous iron(II)-tris(bipyridine) upon excitation into the singlet metal-to-ligand charge-transfer band (1MLCT) has been characterized by femtosecond fluorescence up-conversion and transient absorption (TA) studies. experiment shows a very short-lived broad 1MLCT emission at approximately 600 nm, which decays in < or =20 fs, weak 660 we attribute to 3MLCT, populated intersystem crossing (ISC) from state. TA studies show (<150 fs) excited-state (ESA) below 400...
European XFEL is a free-electron laser (FEL) user facility providing soft and hard X-ray FEL radiation to initially six scientific instruments. Starting operation in fall 2017 will provide new research opportunities users from science domains as diverse physics, chemistry, geo- planetary sciences, materials sciences or biology. The unique feature of the provision high average brilliance regime, combined with pulse properties extreme peak intensities, femtosecond duration degree coherence....
Accurate modeling of the X-ray absorption near-edge spectra (XANES) is required to unravel local structure metal sites in complex systems and their structural changes upon chemical or light stimuli. Two relevant examples are reported here concerning following: (i) effect molecular adsorption on 3d metals hosted inside metal-organic frameworks (ii) induced dynamics spin crossover complexes. In both cases, amount models for simulation can reach a hundred, depending number parameters. Thus,...
It's sizzling! Femtosecond fluorescence-upconversion studies of aqueous [Ru(bpy)3]2+ show a short-lived vibrationally hot emission the singlet metal-to-ligand charge-transfer state, with an ultrafast intersystem crossing (≈10 fs) to triplet state at constant energy (the colors indicate luminescence intensity). Supporting information for this article is available on WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z600125_s.pdf or from author. Please note: The publisher not responsible...
Structural changes of the iron(II)-tris-bipyridine ([Fe(II)(bpy)(3)](2+)) complex induced by ultrashort pulse excitation and population its short-lived (< or =0.6 ns) quintet high spin state have been detected picosecond x-ray absorption spectroscopy. The structural relaxation from to low was followed over entire lifetime excited state. A combined analysis x-ray-absorption near-edge structure extended fine spectroscopy features delivers an Fe-N bond elongation 0.2 in compared singlet ground
X-ray free electron lasers (XFELs) deliver short (<100 fs) and intense (∼10(12) photons) pulses of hard X-rays, making them excellent sources for time-resolved studies. Here we show that, despite the inherent instabilities current (SASE based) XFELs, they can be used measuring high-quality absorption data report femtosecond near-edge spectroscopy (XANES) measurements a spin-crossover system, iron(II) tris(2,2'-bipyridine) in water. The indicate that low-spin to high-spin transition modeled...
Dizzy cooling: Femtosecond excitation of the singlet states aqueous [FeII(bpy)3]2+ (bpy=2,2′-bipyridine) leads to formation a vibrationally hot quintet state that exhibits wave-packet dynamics arising from chelate-ring and bending mode. The vibrational relaxation involves at least two modes: FeN stretching mode (see picture) coherently excited mode, which relax on different time scales.
L(2,3) X-ray absorption spectra of aqueous [Ru(II)(bpy)3]2+ have been recorded in its ground and excited states, 50 ps after short pulse laser excitation. Significant changes both the XANES (X-ray Near-Edge Absorption Structure) EXAFS (Extended Fine regions state complex are detected. The line shapes quantitatively simulated using a crystal field multiplet code trigonal symmetry. In addition, spectral region states analyzed order to extract structural parameters their corresponding molecular...
The ability to visualize molecular structure in the course of a chemical reaction or biological function has been dream scientists for decades. X-ray absorption spectroscopy (XAS) is ideal this respect because it chemically selective and can be implemented any type medium. Furthermore, using near-edge (XANES) extended fine (EXAFS) laser pump/X-ray probe experiments allows retrieval not only local geometric system under study, but also underlying electronic changes that drive structural...
Abstract Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission diffuse scattering at SACLA facility track non-equilibrated electronic structural dynamics within a bimetallic donor–acceptor complex that contains...
We have studied the photoinduced low spin (LS) to high (HS) conversion of [Fe(bipy)3]2+ in aqueous solution. In a laser pump/X-ray probe synchrotron setup permitting simultaneous, time-resolved X-ray diffuse scattering (XDS) and spectroscopic measurements at 3.26 MHz repetition rate, we observed interplay between intramolecular dynamics intermolecular caging solvent response with better than 100 ps time resolution. On this scale, initial ultrafast transition associated geometric structure...
We study the structural dynamics of photoexcited $[\mathrm{Co}(\text{terpy}{)}_{2}{]}^{2+}$ in an aqueous solution with ultrafast x-ray diffuse scattering experiments conducted at Linac Coherent Light Source. Through direct comparisons density functional theory calculations, our analysis shows that photoexcitation event leads to elongation Co-N bonds, followed by coherent bond length oscillations arising from impulsive excitation a vibrational mode dominated symmetrical stretch all six...
In liquid phase chemistry dynamic solute-solvent interactions often govern the path, ultimate outcome, and efficiency of chemical reactions. These steps involve many-body movements on subpicosecond time scales thus ultrafast structural tools capable capturing both intramolecular electronic changes, local solvent changes are desired. We have studied intra- intermolecular dynamics a model chromophore, aqueous [Fe(bpy)3](2+), with complementary X-ray in single experiment exploiting intense XFEL...
Accurate determination of the transient electronic structures, which drive photochemical reactions, is crucial in chemistry and biology. We report detection chemical changes on picosecond time scale by x-ray-absorption near-edge structure photoexcited aqueous [Ru(bpy)(3)](2+). Upon ultrashort laser pulse excitation a charge transfer excited state having 300 ns lifetime formed. detect change oxidation central Ru atom at its L3 L2 edges, temporal resolution 100 ps with zero unambiguously determined.
Metallica: A large contraction of the Pt-Pt bond in triplet excited state photoreactive [Pt(2)(P(2)O(5)H(2))(4)](4-) ion is determined by time-resolved X-ray absorption spectroscopy (see picture). The strengthening interaction accompanied a weakening ligand coordination bonds, resulting an elongation platinum-ligand that for first time.
Ultrafast spin probe: A short-lived transient species of light-excited [Fe(bpy)3]2+ (bpy=2,2′-bipyridine) shows geometry variations that correspond to excitation a high-spin state, in which the momentum FeII has now been directly determined be S=2 by spin-sensitive ultrafast X-ray emission spectroscopy. Detailed facts importance specialist readers are published as "Supporting Information". Such documents peer-reviewed, but not copy-edited or typeset. They made available submitted authors....
Theoretical predictions show that depending on the populations of Fe 3d xy , xz and yz orbitals two possible quintet states can exist for high-spin state photoswitchable model system [Fe(terpy)2]2+. The differences in structure molecular properties these 5B2 5E quintets are very small pose a substantial challenge experiments to resolve them. Yet better understanding physics this system, which lead design novel molecules with enhanced photoswitching performance, it is vital determine reached...
Reaction pathways of biochemical processes are influenced by the dissipative electrostatic interaction reagents with solvent water molecules. The simulation these interactions requires a parametrization permanent and induced dipole moments. However, underlying molecular polarizability its dependence on ions partially unknown. Here, we apply intense terahertz pulses to liquid water, whose oscillations match timescale orientational relaxation. Using combination pump / optical probe...
Abstract Disentangling the strong interplay between electronic and nuclear degrees of freedom is essential to achieve a full understanding excited state processes during ultrafast nonadiabatic chemical reactions. However, complexity multi-dimensional potential energy surfaces means that this remains challenging. The flow vibrational relaxation can be explored with structural sensitivity by probing wavepacket using femtosecond time-resolved X-ray Absorption Near Edge Structure (TR-XANES). it...