Robin Y. Engel
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View article: Insight into the Carbon Monoxide Reduction Reaction on Cu(111) from <i>Operando</i> Electrochemical X‐ray Photoelectron Spectroscopy
Insight into the Carbon Monoxide Reduction Reaction on Cu(111) from <i>Operando</i> Electrochemical X‐ray Photoelectron Spectroscopy Open
In this work, we introduce a modified dip‐and‐pull electrochemical X‐ray photoelectron spectroscopy (ECXPS) approach that offers new mechanistic insight into the alkaline carbon monoxide reduction reaction (CORR) over a Cu(111) single crys…
View article: Spectroscopic Survey of Selectivity Trends in Syngas Conversion over Single Crystal Catalysts
Spectroscopic Survey of Selectivity Trends in Syngas Conversion over Single Crystal Catalysts Open
The sustainability transition of the chemical industry hinges on the educated design of catalysts for reactions such as the CO hydrogenation, optimizing the materials for selectivity toward valuable products. So far, theoretical models hav…
View article: Poleval: A Python package for HAXPES analysis
Poleval: A Python package for HAXPES analysis Open
POLEVAL provides a software toolbox for collaborative, persistent and reproducible analysis of XPS experiments. It allows to treat, analyse and visualise the results of an extended experimental campaign in a single python notebook in a con…
View article: Time-resolved soft X-ray methods on solids with the MUSIX endstation ‒ Recent upgrades for geometric flexibility
Time-resolved soft X-ray methods on solids with the MUSIX endstation ‒ Recent upgrades for geometric flexibility Open
In recent years, the mu lti-dimensional s pectroscopy and i nelastic X -ray scattering endstation MUSIX has become an extensively used instrument at the XUV/soft X-ray free-electron laser FLASH and the synchrotron source PETRA III at DESY …
View article: Simultaneous mapping of the ultrafast time and fluence dependence of the laser-induced insulator-to-metal transition in magnetite
Simultaneous mapping of the ultrafast time and fluence dependence of the laser-induced insulator-to-metal transition in magnetite Open
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 to probe with high chemical selectivity and at atom…
View article: Insight into the carbon monoxide reduction reaction on Cu(111) from operando electrochemical X-ray photoelectron spectroscopy
Insight into the carbon monoxide reduction reaction on Cu(111) from operando electrochemical X-ray photoelectron spectroscopy Open
In this work, we introduce a modified dip-and-pull ECXPS approach that offers new mechanistic insight into the alkaline CORR over a Cu(111) single crystal surface. We tackle two major unresolved questions in the CORR mechanism that persist…
View article: Simultaneous mapping of the ultrafast time and fluence dependence of the laser-induced insulator-to-metal transition in magnetite
Simultaneous mapping of the ultrafast time and fluence dependence of the laser-induced insulator-to-metal transition in magnetite Open
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 to probe with high chemical selectivity and at atom…
View article: Mechanistic Insights into Ni₅Ga₃ Thin Film Catalysts: An Ambient Pressure XPS and DFT Study
Mechanistic Insights into Ni₅Ga₃ Thin Film Catalysts: An Ambient Pressure XPS and DFT Study Open
The intermetallic compound δ-Ni₅Ga₃ has emerged as a promising catalyst for CO2 hydrogenation to methanol, offering low-pressure operation, high selectivity, and enhanced stability compared to conventional Cu/ZnO catalysts. However, the fu…
View article: Analysis of long-lived effects in high-repetition-rate stroboscopic transient X-ray absorption experiments on thin films
Analysis of long-lived effects in high-repetition-rate stroboscopic transient X-ray absorption experiments on thin films Open
Time-resolved X-ray absorption spectroscopy (tr-XAS) has been shown to be a versatile measurement technique for investigating non-equilibrium dynamics. Novel X-ray free electron laser (XFEL) facilities like the European XFEL offer increase…
View article: Protocols for x-ray transient grating pump/optical probe experiments at x-ray free electron lasers
Protocols for x-ray transient grating pump/optical probe experiments at x-ray free electron lasers Open
Transient grating spectroscopy is a specialized application of the four-wave-mixing methodology and constitutes a versatile technique for investigating the dynamics of vibrational, magnetic and electronic degrees of freedom of matter in a …
View article: A compact approach to higher-resolution resonant inelastic x-ray scattering detection using photoelectrons
A compact approach to higher-resolution resonant inelastic x-ray scattering detection using photoelectrons Open
The detection of inelastically scattered soft x-rays with high energy resolution usually requires large grating spectrometers. Recently, photoelectron spectrometry for analysis of x-rays (PAX) has been rediscovered for modern spectroscopy …
View article: Optical control of 4 <i>f</i> orbital state in rare-earth metals
Optical control of 4 <i>f</i> orbital state in rare-earth metals Open
A change of orbital state alters the coupling between ions and their surroundings drastically. Orbital excitations are hence key to understand and control interaction of ions. Rare-earth elements with strong magneto-crystalline anisotropy …
View article: A numerical study of the anisotropic distribution of γ-ray emission from oriented <sup>129m,131m,133m</sup>Xe
A numerical study of the anisotropic distribution of γ-ray emission from oriented <sup>129m,131m,133m</sup>Xe Open
Spin-polarized radioactive nuclei emit radioactive decay products in an anisotropic manner that is characteristic of their degree of nuclear orientation. This property can be utilized for nuclear magnetic resonance spectroscopy and imaging…
View article: Electron population dynamics in resonant non-linear x-ray absorption in nickel at a free-electron laser
Electron population dynamics in resonant non-linear x-ray absorption in nickel at a free-electron laser Open
Free-electron lasers provide bright, ultrashort, and monochromatic x-ray pulses, enabling novel spectroscopic measurements not only with femtosecond temporal resolution: The high fluence of their x-ray pulses can also easily enter the regi…
View article: The interplay of local electron correlations and ultrafast spin dynamics in fcc Ni
The interplay of local electron correlations and ultrafast spin dynamics in fcc Ni Open
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. The interplay between the respective terms of the H…
View article: Photo-induced charge-transfer renormalization in NiO
Photo-induced charge-transfer renormalization in NiO Open
Photo-doped states in strongly correlated charge transfer insulators are characterized by $d$-$d$ and $d$-$p$ interactions and the resulting intertwined dynamics of charge excitations and local multiplets. Here we use femtosecond x-ray abs…
View article: Photon-shot-noise-limited transient absorption soft X-ray spectroscopy at the European XFEL
Photon-shot-noise-limited transient absorption soft X-ray spectroscopy at the European XFEL Open
Femtosecond transient soft X-ray absorption spectroscopy (XAS) is a very promising technique that can be employed at X-ray free-electron lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here, a ded…
View article: Photon-shot-noise-limited transient absorption soft X-ray spectroscopy at the European XFEL
Photon-shot-noise-limited transient absorption soft X-ray spectroscopy at the European XFEL Open
Femtosecond transient soft X-ray absorption spectroscopy (XAS) is a very promising technique that can be employed at X-ray free-electron lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here, a ded…
View article: Electron Dynamics at High-Energy Densities in Nickel from Non-linear Resonant X-ray Absorption Spectra
Electron Dynamics at High-Energy Densities in Nickel from Non-linear Resonant X-ray Absorption Spectra Open
The pulse intensity from X-ray free-electron lasers (FELs) can create extreme excitation densities in solids, entering the regime of non-linear X-ray-matter interactions. We show L3-edge absorption spectra of metallic nickel thin films wit…
View article: A Rate Model of Electron Populations for Non-linear High-Fluence X-ray Absorption Near-Edge Spectra
A Rate Model of Electron Populations for Non-linear High-Fluence X-ray Absorption Near-Edge Spectra Open
Absorbing a focused, femtosecond X-ray pulse from a Free-Electron Laser (FEL) can lead to extreme electronic excitations in solids. This excitation drives changes of the electronic system over the course of the pulse duration and the overa…
View article: Ultrafast modification of the electronic structure of a correlated insulator
Ultrafast modification of the electronic structure of a correlated insulator Open
A nontrivial balance between Coulomb repulsion and kinematic effects determines the electronic structure of correlated electron materials. The use of electromagnetic fields strong enough to rival these native microscopic interactions allow…
View article: Probing electron and hole colocalization by resonant four-wave mixing spectroscopy in the extreme ultraviolet
Probing electron and hole colocalization by resonant four-wave mixing spectroscopy in the extreme ultraviolet Open
Extending nonlinear spectroscopic techniques into the x-ray domain promises unique insight into photoexcited charge dynamics, which are of fundamental and applied interest. We report on the observation of a third-order nonlinear process in…
View article: Data for: Probing electron and hole co-localization by resonant four-wave mixing spectroscopy in the extreme-ultraviolet
Data for: Probing electron and hole co-localization by resonant four-wave mixing spectroscopy in the extreme-ultraviolet Open
Data for: Probing electron and hole co-localization by resonant four-wave mixing spectroscopy in the extreme-ultraviolet
View article: Data for: Probing electron and hole co-localization by resonant four-wave mixing spectroscopy in the extreme-ultraviolet
Data for: Probing electron and hole co-localization by resonant four-wave mixing spectroscopy in the extreme-ultraviolet Open
Data for: Probing electron and hole co-localization by resonant four-wave mixing spectroscopy in the extreme-ultraviolet
View article: Ultrafast manipulation of the NiO antiferromagnetic order via sub-gap optical excitation
Ultrafast manipulation of the NiO antiferromagnetic order via sub-gap optical excitation Open
Wide-band-gap insulators such as NiO offer the exciting prospect of coherently manipulating electronic correlations with strong optical fields. Contrary to metals where rapid dephasing of optical excitation via electronic processes occurs,…
View article: Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL
Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL Open
Femtosecond transient soft X-ray Absorption Spectroscopy (XAS) is a very promising technique that can be employed at X-ray Free Electron Lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here we pre…
View article: Ultrafast manipulation of the NiO antiferromagnetic order <i>via</i> sub-gap optical excitation
Ultrafast manipulation of the NiO antiferromagnetic order <i>via</i> sub-gap optical excitation Open
We present a comprehensive investigation of ultrafast demagnetisation and accompanying band gap reduction in a charge transfer insulator using time-resolved resonant X-ray reflectivity.
View article: Optical control of 4f orbital state in rare-earth metals
Optical control of 4f orbital state in rare-earth metals Open
A change of orbital state alters the coupling between ions and their surroundings drastically. Orbital excitations are hence key to understand and control interaction of ions. Rare-earth (RE) elements with strong magneto-crystalline anisot…