Refine
Year of publication
Document Type
- Article (108)
- Postprint (11)
- Other (4)
- Monograph/Edited Volume (1)
- Preprint (1)
Is part of the Bibliography
- yes (125)
Keywords
- RIXS (5)
- Resonant inelastic X-ray scattering (5)
- photochemistry (5)
- spectroscopy (5)
- Electron spectroscopy (3)
- X-ray emission spectroscopy (3)
- charge-transfer (3)
- nitrogen (3)
- photoelectron spectroscopy (3)
- spectra (3)
- Artof (2)
- Molecules (2)
- Nitrogen (2)
- Photochemie (2)
- Photoelectron spectroscopy (2)
- Protonierung (2)
- Pump-probe (2)
- RIXS (resonant inelastic X-ray scattering) (2)
- RIXS (resonante inelastische Röntgenstreuung) (2)
- Selektiver Bindungsbruch (2)
- Stickstoff (2)
- Surface science (2)
- Synchrotron (2)
- Time of flight (2)
- X-ray absorption spectroscopy (2)
- X-ray spectroscopy (2)
- XAS (2)
- XES (2)
- basis-sets (2)
- complexes (2)
- dichalcogenides (2)
- dynamics (2)
- electron spectroscopy (2)
- electronic-structure (2)
- iron (2)
- photoelectron (2)
- protonation (2)
- pump-probe (2)
- raman-scattering (2)
- selective bond cleavage (2)
- states (2)
- water (2)
- 6H-SiC (1)
- APECS (1)
- ARPES (1)
- ARTOF (1)
- Anions (1)
- Aqueous solution (1)
- Auger electron (1)
- CM(-1) (1)
- CO desorption (1)
- CU(110) (1)
- Cations (1)
- Charge-transfer state (1)
- Condensed matter physics (1)
- Core-hole clock (1)
- Covalent interaction (1)
- Density functional theory (1)
- Electron-phonon coupling (1)
- Electronic structure (1)
- Energy (1)
- Energy resolution (1)
- Equilibrium (1)
- FE (1)
- Free electron laser (1)
- Free-electron laser (1)
- Free-electron-laser science (1)
- Gas phase (1)
- High transmission micro focus beamline (1)
- Ligand-field state (1)
- Ligands (1)
- Liquid Jet (1)
- Liquids (1)
- Metals (1)
- Molecular dynamics (1)
- Molecular structure (1)
- NM (1)
- Near edge X-ray absorption fine structure (1)
- Ni (1)
- Nonlinear X-ray spectroscopy (1)
- Nuclear physics (1)
- Oxygen (1)
- Phase transitions (1)
- Plane grating emission spectrometer (1)
- Potential of mean force (1)
- Pulse induced transparency (1)
- RIXS at FELs (1)
- Scattering breakdown (1)
- Semiconductors (1)
- Silicon carbide (1)
- Soft X-ray monochromator (1)
- Solvents (1)
- Stimulated scattering (1)
- Storage rings (1)
- Synchrotron Radiation (1)
- Synchrotron radiation (1)
- Transition-metal ion (1)
- Two-temperature model (1)
- Ultrafast (1)
- Ultrafast spectroscopy (1)
- Ultrafast surface science (1)
- Wide angle (1)
- X-ray Spectroscopy (1)
- X-ray absorption (1)
- X-ray scattering (1)
- XMCD (1)
- ab initio (1)
- ab-initio (1)
- absorption-spectra (1)
- anti-Stokes resonant x-ray raman scattering (1)
- atomic multiplet (1)
- auger spectrum (1)
- catalysis (1)
- chemistry (1)
- coating (1)
- coincidence (1)
- collapse (1)
- continuous distribution model (1)
- density (1)
- density functional calculations (1)
- electron localization (1)
- electron-phonon scattering (1)
- emission (1)
- energy resolution (1)
- energy-conversion (1)
- excited state selectivity (1)
- excited-state proton-transfer (1)
- fast dissociation (1)
- femtosecond slicing (1)
- free electron lasers (1)
- halo (1)
- hydrogen evolution reaction (1)
- hydroxypyridine-pyridone (1)
- instrumentation (1)
- intersystem crossing (1)
- ion migration (1)
- iron complexes (1)
- iron cyanides (1)
- iron(II) (1)
- l-edge xas (1)
- laser illumination (1)
- lead halide perovskite (1)
- ligand (1)
- liquid water (1)
- manganese (1)
- mean-field model (1)
- molecular-structure (1)
- molecule (1)
- oxygen/Ag(111) (1)
- phase separation (1)
- phase transition (1)
- phase transitions (1)
- photosystem-II (1)
- potential ene rgy surface (1)
- potential-energy surface (1)
- probe (1)
- protomeric equilibria (1)
- ray-emission-spectroscopy (1)
- relaxation dynamics (1)
- resonant inelastic x-ray scattering (1)
- self-association (1)
- simulations (1)
- soft X-ray absorption (1)
- solvation (1)
- space-charge effects (1)
- spectrum (1)
- spin-crossover (1)
- spin-state (1)
- stability (1)
- stochastic quench (1)
- structure of water (1)
- surface science (1)
- synchrotron (1)
- time of flight (1)
- time-resolved (1)
- tranfer excited-state (1)
- ultrafast (1)
- ultrafast photochemistry (1)
- valence (1)
- vapor (1)
- vibrational structure (1)
- water-oxidation (1)
- water-vapor (1)
- wide angle (1)
- x-ray (1)
- x-ray photoemission (1)
- x-ray-absorption (1)
X-ray spectroscopy is a powerful tool to study the local charge distribution of chemical systems. Together with the liquid jet it becomes possible to probe chemical systems in their natural environment, the liquid phase. In this work, we present X-ray absorption (XA), X-ray emission (XE) and resonant inelastic X-ray scattering (RIXS) data of pure water and various salt solutions and show the possibilities these methods offer to elucidate the nature of ion-water interaction.
In the current work, X-ray emission spectra of aqueous solutions of different inorganic salts within the Hofmeister series are presented. The results reflect the direct interaction of the ions with the water molecules and therefore, reveal general properties of the salt-water interactions. Within the experimental precision a significant effect of the ions on the water structure has been observed but no ordering according to the structure maker/structure breaker concept could be mirrored in the results indicating that the Hofmeister effect if existent may be caused by more complex interactions.
Hydration shells around ions are crucial for many fundamental biological and chemical processes. Their local physicochemical properties are quite different from those of bulk water and hard to probe experimentally. We address this problem by combining soft X-ray spectroscopy using a liquid jet and molecular dynamics (MD) simulations together with ab initio electronic structure calculations to elucidate the water ion interaction in a MgCl2 solution at the molecular level. Our results reveal that salt ions mainly affect the electronic properties of water molecules in close vicinity and that the oxygen K-edge X-ray emission spectrum of water molecules in the first solvation shell differs significantly from that of bulk water. Ion-specific effects are identified by fingerprint features in the water X-ray emission spectra. While Mg2+ ions cause a bathochromic shift of the water lone pair orbital, the 3p orbital of the Cl- ions causes an additional peak in the water emission spectrum at around 528 eV.
We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5 sigma and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process.
We prove the hitherto hypothesized sequential dissociation of Fe(CO)(5) in the gas phase upon photoexcitation at 266 nm via a singlet pathway with time-resolved valence and core-level photoelectron spectroscopy with an x-ray free-electron laser. Valence photoelectron spectra are used to identify free CO molecules and to determine the time constants of stepwise dissociation to Fe(CO)(4) within the temporal resolution of the experiment and further to Fe(CO)(3) within 3 ps. Fe 3p core-level photoelectron spectra directly reflect the singlet spin state of the Fe center in Fe(CO)(5), Fe(CO)(4), and Fe(CO)(3) showing that the dissociation exclusively occurs along a singlet pathway without triplet-state contribution. Our results are important for assessing intra- and intermolecular relaxation processes in the photodissociation dynamics of the prototypical Fe(CO)(5) complex in the gas phase and in solution, and they establish time-resolved core-level photoelectron spectroscopy as a powerful tool for determining the multiplicity of transition metals in photochemical reactions of coordination complexes. Published by AIP Publishing.
Determining covalent and charge-transfer contributions to bonding in solution has remained an experimental challenge. Here, the quenching of fluorescence decay channels as expressed in dips in the L-edge X-ray spectra of solvated 3d transition-metal ions and complexes was reported as a probe. With a full set of experimental and theoretical ab initio L-edge X-ray spectra of aqueous Cr3+, including resonant inelastic X-ray scattering, we address covalency and charge transfer for this prototypical transition-metal ion in solution. We dissect local atomic effects from intermolecular interactions and quantify X-ray optical effects. We find no evidence for the asserted ultrafast charge transfer to the solvent and show that the dips are readily explained by X-ray optical effects and local atomic state dependence of the fluorescence yield. Instead, we find, besides ionic interactions, a covalent contribution to the bonding in the aqueous complex of ligand-to-metal charge-transfer character.
Transition-metal complexes have long attracted interest for fundamental chemical reactivity studies and possible use in solar energy conversion(1,2). Electronic excitation, ligand loss from the metal centre, or a combination of both, creates changes in charge and spin density at the metal site(3-11) that need to be controlled to optimize complexes for photocatalytic hydrogen production(8) and selective carbon-hydrogen bond activation(9-11). An understanding at the molecular level of how transition-metal complexes catalyse reactions, and in particular of the role of the short-lived and reactive intermediate states involved, will be critical for such optimization. However, suitable methods for detailed characterization of electronic excited states have been lacking. Here we show, with the use of X-ray laser-based femtosecond-resolution spectroscopy and advanced quantum chemical theory to probe the reaction dynamics of the benchmark transition-metal complex Fe(CO)(5) in solution, that the photo-induced removal of CO generates the 16-electron Fe(CO)(4) species, a homogeneous catalyst(12,13) with an electron deficiency at the Fe centre(14,15), in a hitherto unreported excited singlet state that either converts to the triplet ground state or combines with a CO or solvent molecule to regenerate a penta-coordinated Fe species on a sub-picosecond timescale. This finding, which resolves the debate about the relative importance of different spin channels in the photochemistry of Fe(CO)(5) (refs 4, 16-20), was made possible by the ability of femtosecond X-ray spectroscopy to probe frontier-orbital interactions with atom specificity. We expect the method to be broadly applicable in the chemical sciences, and to complement approaches that probe structural dynamics in ultrafast processes.
We report on a combined theoretical and experimental study of core-excitation spectra of gas and liquid phase methanol as obtained with the use of X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). The electronic transitions are studied with computational methods that include strict and extended second-order algebraic diagrammatic construction [ADC(2) and ADC(2)-x], restricted active space second-order perturbation theory, and time-dependent density functional theory-providing a complete assignment of the near oxygen K-edge XAS. We show that multimode nuclear dynamics is of crucial importance for explaining the available experimental XAS and RIXS spectra. The multimode nuclear motion was considered in a recently developed "mixed representation" where dissociative states and highly excited vibrational modes are accurately treated with a time-dependent wave packet technique, while the remaining active vibrational modes are described using Franck-Condon amplitudes. Particular attention is paid to the polarization dependence of RIXS and the effects of the isotopic substitution on the RIXS profile in the case of dissociative core-excited states. Our approach predicts the splitting of the 2a RIXS peak to be due to an interplay between molecular and pseudo-atomic features arising in the course of transitions between dissociative core- and valence-excited states. The dynamical nature of the splitting of the 2a peak in RIXS of liquid methanol near pre-edge core excitation is shown. The theoretical results are in good agreement with our liquid phase measurements and gas phase experimental data available from the literature. (C) 2019 Author(s).
A scheme for simulations of resonant inelastic X-ray scattering (RIXS) cross-sections within time-dependent density functional theory (TD-DFT) applying the restricted subspace approximation (RSA) is presented. Therein both occupied core and valence Kohn-Sham orbitals are included in the donor-space, while the accepting virtual orbital space in the linear response TD-DFT equations is restricted to efficiently compute both the valence- and core-excited states of the many electron system. This yields a consistent description of all states contributing to the RIXS scattering process within a single calculation. The introduced orbital truncation allows to automatize the method and facilitates RIXS simulations for systems considerably larger than ones accessible with wave-function based methods. Using the nitrogen K-edge RIXS spectra of 2-thiopyridone and its deprotonated anion as a showcase, the method is benchmarked for different exchange-correlation functionals, the impact of the RSA is evaluated, and the effects of explicit solvation are discussed. Improvements compared to simulations in the frozen orbital approximation are also assessed. The general applicability of the framework is further tested by comparison to experimental data from the literature. The use of TD-DFT core-excited states to the calculation of vibrationally resolved RIXS spectra is also investigated by combining potential energy scans along relevant coordinates with wave packet simulations.
In this combined theoretical and experimental study we report a full analysis of the resonant inelastic X-ray scattering (RIXS) spectra of H2O, D2O and HDO. We demonstrate that electronically-elastic RIXS has an inherent capability to map the potential energy surface and to perform vibrational analysis of the electronic ground state in multimode systems. We show that the control and selection of vibrational excitation can be performed by tuning the X-ray frequency across core-excited molecular bands and that this is clearly reflected in the RIXS spectra. Using high level ab initio electronic structure and quantum nuclear wave packet calculations together with high resolution RIXS measurements, we discuss in detail the mode coupling, mode localization and anharmonicity in the studied systems.