A5003359665- X-ray Spectroscopy and Fluorescence Analysis
- Advanced X-ray Imaging Techniques
- Electron and X-Ray Spectroscopy Techniques
- Advanced Chemical Physics Studies
- Advanced Electron Microscopy Techniques and Applications
- X-ray Diffraction in Crystallography
- Magnetism in coordination complexes
- Laser-Matter Interactions and Applications
- High-pressure geophysics and materials
- Crystallography and Radiation Phenomena
- Magnetic properties of thin films
- Electronic and Structural Properties of Oxides
- Advanced MRI Techniques and Applications
- Mass Spectrometry Techniques and Applications
- Atomic and Molecular Physics
- Particle Accelerators and Free-Electron Lasers
- Molecular spectroscopy and chirality
- Material Dynamics and Properties
- Transition Metal Oxide Nanomaterials
- Catalytic Processes in Materials Science
- Porphyrin and Phthalocyanine Chemistry
- Diamond and Carbon-based Materials Research
- Iron oxide chemistry and applications
- Magnetic and transport properties of perovskites and related materials
- Semiconductor materials and devices
Deutsches Elektronen-Synchrotron DESY
2018-2025
European X-Ray Free-Electron Laser
2020-2024
Fritz Haber Institute of the Max Planck Society
2022
RWTH Aachen University
2021
Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy
2021
Yonsei University
2021
Universität Hamburg
2020-2021
Paul Scherrer Institute
2021
Helmholtz-Zentrum Berlin für Materialien und Energie
2013-2020
Center for Free-Electron Laser Science
2020
The effective spin sum rule is widely used in the quantitative analysis of x-ray magnetic circular dichroism spectra. Here, this important, though imperfect, reviewed with a detailed various sources for errors and deviations. simulations confirm that final state effects core level spin-orbit coupling core-valence exchange interactions (multiplet effects) are linearly related sum-rule error. Within charge transfer multiplet approach, we have analyzed these effects, combination affecting...
We investigate the interaction of TbPc(2) single molecule magnets (SMMs) with ferromagnetic Ni substrates. Using element-resolved x-ray magnetic circular dichroism, we show that couples antiferromagnetically to films through ligand-mediated superexchange. This coupling is strongly anisotropic and can be manipulated by doping interface electron acceptor or donor atoms. observe relative orientation substrate anisotropy axes critically affects SMM behavior. complexes deposited on...
We investigate the hierarchy of local correlation and hybridization effects in metal-organic molecules adsorbed on metals. Using x-ray magnetic circular dichroism ligand field multiplet calculations, we demonstrate that 3$d$ electronic ground state monolayer metal-phthalocyanine (CoPc, FePc) Au(111) is given by coherent superposition two charge states, ${d}^{n}E+{d}^{n+1}$, where $E$ represents a substrate electron antiferromagnetically coupled to central metal ion ${d}^{n}$ many-body ionic...
The valence-excited states of ferric and ferrous hexacyanide ions in aqueous solution were mapped by resonant inelastic X-ray scattering (RIXS) at the Fe L2,3 N K edges. Probing both central ligand atoms enabled identification metal- ligand-centered excited states, as well ligand-to-metal metal-to-ligand charge-transfer states. Ab initio calculations utilizing RASPT2 method used to simulate L2,3-edge RIXS spectra quantification covalencies occupied empty orbitals π σ symmetry. We found that...
Carrier dynamics affects photocatalytic systems, but direct and real-time observations in an element-specific energy-level-specific manner are challenging. In this study, we demonstrate that the of photo-generated holes metal oxides can be directly probed by using femtosecond X-ray absorption spectroscopy at free-electron laser. We identify energy level life time with a long (230 pico-seconds) nano-crystal materials. also observe trapped show distribution bandgap region formation 0.3...
The complex electronic structure of metallic ferromagnets is determined by a balance between exchange interaction, electron hopping leading to band formation, and local Coulomb repulsion. By combining high energy temporal resolution in femtosecond time-resolved X-ray absorption spectroscopy with ab initio time-dependent density functional theory we analyze the fcc Ni on time scale these interactions pump-probe experiment. We distinguish transient broadening shifts spectra, which demonstrate...
The charge and spin-state evolution of manganese cobalt in the LaMn1–xCoxO3 (x = 0.00, 0.25, 0.50, 0.75, 1.00) perovskite nanoparticles have been studied with soft X-ray absorption spectroscopy. results show a gradual increase average oxidation state both Mn Co ions doping. valence samples remains close to 3.0, increasing from 3.1 4.0 2.0 3.0. symmetry was determined using multiplet calculations. Calculating intensity-area oxygen K pre-edge feature confirmed an covalency state. ground-state...
The SASE3 soft X-ray beamline at the European XFEL has been designed and built to provide experiments with a pink or monochromatic beam in photon energy range 250–3000 eV. Here, focus is operation of beamline, design performance grating monochromator are reported. unique capability free-electron laser source produce short femtosecond pulses high degree coherence challenges by demanding control both temporal resolution. aim transport close transform-limited poses very demands on optics...
Cobalt phthalocyanine (CoPc) and iron (FePc) are possible oxygen reduction catalysts in fuel cells, but the exact functioning deactivation of these is unknown. The electronic structure CoPc FePc has been studied situ under hydrogen atmospheres by a combination ambient-pressure X-ray photoelectron spectroscopy absorption spectroscopy. results show that when introduced, changes oxidation state while cobalt does not. data binds an end-on configuration CoPc, for side-on binding most likely.
Liquid water molecules interact strongly with each other, forming a fluctuating hydrogen bond network and thereby giving rise to the anomalous phase diagram of liquid water. Consequently, symmetric asymmetric have been found in picosecond time average IR optical Raman spectroscopy. With subnatural linewidth resonant inelastic x-ray scattering (RIXS) at vibrational resolution, we take sub-femtosecond snapshots electronic structural properties network. We derive strong dominance nonsymmetric...
Abstract Thermally driven chemistry as well materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes central and powerful concept in physics, materials science. However, direct experimental access to locally around atomic centers its long-range structure lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized determine state surfaces detect changes...
Femtosecond transient soft X-ray absorption spectroscopy (XAS) is a very promising technique that can be employed at free-electron lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here, dedicated setup X-rays available the Spectroscopy Coherent Scattering (SCS) instrument European Free-Electron Laser (European XFEL) presented. It consists of beam-splitting off-axis zone plate (BOZ) used in transmission create three copies incoming beam, which are...
Abstract The femtosecond excited‐state dynamics following resonant photoexcitation enable the selective deformation of N−H and N−C chemical bonds in 2‐thiopyridone aqueous solution with optical or X‐ray pulses. In combination multiconfigurational quantum‐chemical calculations, orbital‐specific electronic structure its ultrafast accessed inelastic scattering at N 1s level using synchrotron radiation soft free‐electron laser LCLS provide direct evidence for this controlled photoinduced...
The prototypical photoinduced dissociation of Fe(CO)5 in the gas phase is used to test time-resolved x-ray photoelectron spectroscopy for studying photochemical reactions. Upon one-photon excitation at 266 nm, successively dissociates Fe(CO)4 and Fe(CO)3 along a pathway where both fragments retain singlet multiplicity Fe(CO)5. free-electron laser FLASH probe reaction intermediates with valence core-level spectroscopy, experimental results are interpreted ab initio quantum chemical...
Pump-probe methods are a ubiquitous tool in the field of ultrafast dynamic measurements. In recent years, X-ray free-electron laser experiments have gained importance due to their ability probe with high chemical selectivity and at atomic length scales. To obtain complete information, measurements typically repeated many thousands times varying delay and/or fluence settings. This generally necessitates that sample fully recovers before subsequent excitation pulses induced evolution...
Pump-probe methods are a ubiquitous tool in the field of ultrafast dynamic measurements. In recent years, x-ray free-electron laser experiments have gained importance due to their ability probe with high chemical selectivity and at atomic length scales. Measurements typically repeated many thousands times collect sufficient statistics vary parameters like delay or fluence, necessitating that initial conditions restored each time. An alternative is presented by which measure relevant single...
Bonding of the Ni(2+)(aq) complex is investigated with an unprecedented combination resonant inelastic X-ray scattering (RIXS) measurements and ab initio calculations at Ni L absorption edge. The spectra directly reflect relative energies ligand-field charge-transfer valence-excited states. They give element-specific access atomic resolution to ground-state electronic structure allow quantification strength 3d-3d electron correlation interactions in complex. experimentally determined 10Dq =...
In resonant inelastic soft x-ray scattering (RIXS) from molecular and liquid systems, the interplay of ground state structural core-excited dynamical contributions leads to complex spectral shapes that partially allow for ambiguous interpretations. this work, we dissect these in oxygen K-edge RIXS alcohols. We use into electronic as an accurate measure nuclear dynamics intermediate process. determine characteristic time until give a measurable contribution profiles τdyn = 1.2 ± 0.8 fs. By...
Nanoconfined LiBH<sub>4</sub> has been studied <italic>in situ</italic> with X-ray Raman spectroscopy. With 1 bar of hydrogen, partial re-hydrogenation can be achieved.
Extending nonlinear spectroscopic techniques into the x-ray domain promises unique insight photoexcited charge dynamics, which are of fundamental and applied interest. We report on observation a third-order process in lithium fluoride (LiF) at free-electron laser. Exploring yield four-wave mixing (FWM) resonance with transitions to strongly localized core exciton states versus delocalized Bloch states, we find resonant FWM be sensitive probe for degree localization: Substantial sum-...
A change of orbital state alters the coupling between ions and their surroundings drastically. Orbital excitations are hence key to understand control interaction ions. Rare-earth elements with strong magneto-crystalline anisotropy (MCA) important ingredients for magnetic devices. Thus, localized 4
3d transition metal ions, like Fe(II) in a planar organic environment are subject to the details of ligand coordination. In this study orbital splitting D4h symmetry is investigated for using charge transfer multiplet program. By variation 10Dq, Ds and Dt crystal field parameters, orbitals split differently giving rise different spin multiplicity. The relative occupations yield range ground states. Experimental x-ray absorption spectra FePc powder compared with theoretical simulations,...
First principles calculations are performed for the interpretation of L 2,3 x-ray absorption spectrum calcium oxide and fluoride.The first based on configuration interaction (CI) using fully relativistic molecular spinors.The results compared to experimental data also a semi-empirical crystal field multiplet model multichannel multiple scattering method.We show that CI good agreement with experiment, both bulk surface experiments.The remaining differences experiment between theoretical...