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Engel RY, Alexander O, Atak K, Bovensiepen U, Buck J, Carley R, Cascella M, Chardonnet V, Chiuzbaian GS, David C, Döring F, Eschenlohr A, Gerasimova N, de Groot F, Guyader LL, Humphries OS, Izquierdo M, Jal E, Kubec A, Laarmann T, Lambert CH, Lüning J, Marangos JP, Mercadier L, Mercurio G, Miedema PS, Ollefs K, Pfau B, Rösner B, Rossnagel K, Rothenbach N, Scherz A, Schlappa J, Scholz M, Schunck JO, Setoodehnia K, Stamm C, Techert S, Vinko SM, Wende H, Yaroslavtsev AA, Yin Z, Beye M. Electron population dynamics in resonant non-linear x-ray absorption in nickel at a free-electron laser. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2023; 10:054501. [PMID: 37841290 PMCID: PMC10576398 DOI: 10.1063/4.0000206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 09/20/2023] [Indexed: 10/17/2023]
Abstract
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 regime of the non-linear x-ray-matter interaction. Entering this regime necessitates a rigorous analysis and reliable prediction of the relevant non-linear processes for future experiment designs. Here, we show non-linear changes in the L 3 -edge absorption of metallic nickel thin films, measured with fluences up to 60 J/cm2. We present a simple but predictive rate model that quantitatively describes spectral changes based on the evolution of electronic populations within the pulse duration. Despite its simplicity, the model reaches good agreement with experimental results over more than three orders of magnitude in fluence, while providing a straightforward understanding of the interplay of physical processes driving the non-linear changes. Our findings provide important insights for the design and evaluation of future high-fluence free-electron laser experiments and contribute to the understanding of non-linear electron dynamics in x-ray absorption processes in solids at the femtosecond timescale.
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Affiliation(s)
| | - Oliver Alexander
- Department of Physics, Imperial College London, London, United Kingdom
| | - Kaan Atak
- Deutsches Elektronen-Synchrotron DESY, Germany
| | | | | | | | | | - Valentin Chardonnet
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement LCPMR, Paris, France
| | - Gheorghe Sorin Chiuzbaian
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement LCPMR, Paris, France
| | | | | | - Andrea Eschenlohr
- Faculty of Physics and Center for Nanointegration Duisburg-Essen CENIDE, University of Duisburg-Essen, Duisburg, Germany
| | | | - Frank de Groot
- Debye Institute for Nanomaterials Science, Inorganic Chemistry and Catalysis, Utrecht University, Utrecht, The Netherlands
| | | | | | | | - Emmanuelle Jal
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement LCPMR, Paris, France
| | - Adam Kubec
- Paul Scherrer Institut, Villigen, Switzerland
| | | | | | - Jan Lüning
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
| | | | | | | | | | - Katharina Ollefs
- Faculty of Physics and Center for Nanointegration Duisburg-Essen CENIDE, University of Duisburg-Essen, Duisburg, Germany
| | - Bastian Pfau
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Berlin, Germany
| | | | | | - Nico Rothenbach
- Faculty of Physics and Center for Nanointegration Duisburg-Essen CENIDE, University of Duisburg-Essen, Duisburg, Germany
| | | | | | | | | | | | | | | | | | - Heiko Wende
- Faculty of Physics and Center for Nanointegration Duisburg-Essen CENIDE, University of Duisburg-Essen, Duisburg, Germany
| | | | | | - Martin Beye
- Author to whom correspondence should be addressed:
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2
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Microstructure effects on the phase transition behavior of a prototypical quantum material. Sci Rep 2022; 12:10464. [PMID: 35729245 PMCID: PMC9213476 DOI: 10.1038/s41598-022-13872-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 05/30/2022] [Indexed: 11/08/2022] Open
Abstract
Materials with insulator-metal transitions promise advanced functionalities for future information technology. Patterning on the microscale is key for miniaturized functional devices, but material properties may vary spatially across microstructures. Characterization of these miniaturized devices requires electronic structure probes with sufficient spatial resolution to understand the influence of structure size and shape on functional properties. The present study demonstrates the use of imaging soft X-ray absorption spectroscopy with a spatial resolution better than 2 \documentclass[12pt]{minimal}
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\begin{document}$$\upmu$$\end{document}μm to study the insulator-metal transition in vanadium dioxide thin-film microstructures. This novel technique reveals that the transition temperature for the conversion from insulating to metallic vanadium dioxide is lowered by 1.2 K ± 0.4 K close to the structure edges compared to the center. Facilitated strain release during the phase transition is discussed as origin of the observed behavior. The experimental approach enables a detailed understanding of how the electronic properties of quantum materials depend on their patterning at the micrometer scale.
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Rottke H, Engel RY, Schick D, Schunck JO, Miedema PS, Borchert MC, Kuhlmann M, Ekanayake N, Dziarzhytski S, Brenner G, Eichmann U, von Korff Schmising C, Beye M, Eisebitt S. Probing electron and hole colocalization by resonant four-wave mixing spectroscopy in the extreme ultraviolet. SCIENCE ADVANCES 2022; 8:eabn5127. [PMID: 35594356 PMCID: PMC9122317 DOI: 10.1126/sciadv.abn5127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 04/05/2022] [Indexed: 06/15/2023]
Abstract
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 lithium fluoride (LiF) at a free-electron laser. Exploring the yield of four-wave mixing (FWM) in resonance with transitions to strongly localized core exciton states versus delocalized Bloch states, we find resonant FWM to be a sensitive probe for the degree of charge localization: Substantial sum- and difference-frequency generation is observed exclusively when in a one- or three-photon resonance with a LiF core exciton, with a dipole forbidden transition affecting details of the nonlinear response. Our reflective geometry-based approach to detect FWM signals enables the study of a wide variety of condensed matter sample systems, provides atomic selectivity via resonant transitions, and can be easily scaled to shorter wavelengths at free-electron x-ray lasers.
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Affiliation(s)
- Horst Rottke
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Robin Y. Engel
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
- Department of Physics, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Daniel Schick
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Jan O. Schunck
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
- Department of Physics, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Piter S. Miedema
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Martin C. Borchert
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Marion Kuhlmann
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Nagitha Ekanayake
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | | | - Günter Brenner
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Ulrich Eichmann
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Clemens von Korff Schmising
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Martin Beye
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
- Department of Physics, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Stefan Eisebitt
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
- Technische Universität Berlin, Institut für Optik und Atomare Physik, Straße des 17. Juni 135, 10623 Berlin, Germany
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4
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Uzundal CB, Jamnuch S, Berger E, Woodahl C, Manset P, Hirata Y, Sumi T, Amado A, Akai H, Kubota Y, Owada S, Tono K, Yabashi M, Freeland JW, Schwartz CP, Drisdell WS, Matsuda I, Pascal TA, Zong A, Zuerch M. Polarization-Resolved Extreme-Ultraviolet Second-Harmonic Generation from LiNbO_{3}. PHYSICAL REVIEW LETTERS 2021; 127:237402. [PMID: 34936786 DOI: 10.1103/physrevlett.127.237402] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 08/21/2021] [Accepted: 10/15/2021] [Indexed: 06/14/2023]
Abstract
Second harmonic generation (SHG) spectroscopy ubiquitously enables the investigation of surface chemistry, interfacial chemistry, as well as symmetry properties in solids. Polarization-resolved SHG spectroscopy in the visible to infrared regime is regularly used to investigate electronic and magnetic order through their angular anisotropies within the crystal structure. However, the increasing complexity of novel materials and emerging phenomena hampers the interpretation of experiments solely based on the investigation of hybridized valence states. Here, polarization-resolved SHG in the extreme ultraviolet (XUV-SHG) is demonstrated for the first time, enabling element-resolved angular anisotropy investigations. In noncentrosymmetric LiNbO_{3}, elemental contributions by lithium and niobium are clearly distinguished by energy dependent XUV-SHG measurements. This element-resolved and symmetry-sensitive experiment suggests that the displacement of Li ions in LiNbO_{3}, which is known to lead to ferroelectricity, is accompanied by distortions to the Nb ion environment that breaks the inversion symmetry of the NbO_{6} octahedron as well. Our simulations show that the measured second harmonic spectrum is consistent with Li ion displacements from the centrosymmetric position while the Nb─O bonds are elongated and contracted by displacements of the O atoms. In addition, the polarization-resolved measurement of XUV-SHG shows excellent agreement with numerical predictions based on dipole-induced SHG commonly used in the optical wavelengths. Our result constitutes the first verification of the dipole-based SHG model in the XUV regime. The findings of this work pave the way for future angle and time-resolved XUV-SHG studies with elemental specificity in condensed matter systems.
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Affiliation(s)
- Can B Uzundal
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Sasawat Jamnuch
- ATLAS Materials Science Laboratory, Department of NanoEngineering and Chemical Engineering, University of California, San Diego, La Jolla, California, 92023, USA
| | - Emma Berger
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Clarisse Woodahl
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- University of Florida, Gainesville, Florida 32611, USA
| | - Paul Manset
- Ecole Normale Superieure de Paris, Paris, France
| | - Yasuyuki Hirata
- National Defense Academy of Japan, Yokosuka, Kanagawa 239-8686, Japan
| | - Toshihide Sumi
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Angelique Amado
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Hisazumi Akai
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yuya Kubota
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, (JASRI), 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Shigeki Owada
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, (JASRI), 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Kensuke Tono
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, (JASRI), 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Makina Yabashi
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, (JASRI), 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - John W Freeland
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Craig P Schwartz
- Nevada Extreme Conditions Laboratory, University of Nevada, Las Vegas, Las Vegas, Nevada 89154, USA
| | - Walter S Drisdell
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Iwao Matsuda
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Trans-scale Quantum Science Institute, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Tod A Pascal
- ATLAS Materials Science Laboratory, Department of NanoEngineering and Chemical Engineering, University of California, San Diego, La Jolla, California, 92023, USA
- Materials Science and Engineering, University of California San Diego, La Jolla, California, 92023, USA
- Sustainable Power and Energy Center, University of California San Diego, La Jolla, California, 92023, USA
| | - Alfred Zong
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Michael Zuerch
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Fritz Haber Institute of the Max Planck Society, 14195 Berlin, Germany
- Friedrich Schiller University Jena, 07743 Jena, Germany
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5
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Fabiani G, Bouman MD, Mentink JH. Supermagnonic Propagation in Two-Dimensional Antiferromagnets. PHYSICAL REVIEW LETTERS 2021; 127:097202. [PMID: 34506161 DOI: 10.1103/physrevlett.127.097202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 05/18/2021] [Accepted: 07/15/2021] [Indexed: 06/13/2023]
Abstract
We investigate the propagation of magnons after ultrashort perturbations of the exchange interaction in the prototype two-dimensional Heisenberg antiferromagnet. Using the recently proposed neural quantum states, we predict highly anisotropic spreading in space constrained by the symmetry of the perturbation. Interestingly, the propagation speed at the shortest length scale and timescale is up to 40% higher than the highest magnon velocity. We argue that the enhancement stems from extraordinary strong magnon-magnon interactions, suggesting new avenues for manipulating information transfer on ultrashort length scales and timescales.
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Affiliation(s)
- G Fabiani
- Radboud University, Institute for Molecules and Materials (IMM) Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands
| | - M D Bouman
- Radboud University, Institute for Molecules and Materials (IMM) Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands
| | - J H Mentink
- Radboud University, Institute for Molecules and Materials (IMM) Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands
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Flat Field Soft X-ray Spectrometry with Reflection Zone Plates on a Curved Substrate. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10207210] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We report on the first experimental results obtained with a newly designed instrument for high-resolution soft X-ray spectroscopy, using reflection zone plates (RZPs) on a spherical substrate. The spectrometer was tested with a fluorescence source. High-resolution flat field spectra within ±50% around the design energies were measured at an interval of 150–750 eV, using only two RZPs: the first RZP, with its design energy of 277 eV, covered the band of 150–370 eV, and the second RZP, with a design energy of 459 eV, covered the band of 350–750 eV, where the upper boundary of this energy range was defined by the Ni coating of the RZPs. The absolute quantum efficiency of the spectrometer, including the optical element and the detector, was, on average, above 10%, and reached 20% at the designed energies of the RZPs. The resolving power E/∆E exceeded 600 for energies E inside the core range of 200–550 eV.
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7
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Parallel Broadband Femtosecond Reflection Spectroscopy at a Soft X-Ray Free-Electron Laser. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10196947] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
X-ray absorption spectroscopy (XAS) and the directly linked X-ray reflectivity near absorption edges yield a wealth of specific information on the electronic structure around the resonantly addressed element. Observing the dynamic response of complex materials to optical excitations in pump–probe experiments requires high sensitivity to small changes in the spectra which in turn necessitates the brilliance of free electron laser (FEL) pulses. However, due to the fluctuating spectral content of pulses generated by self-amplified spontaneous emission (SASE), FEL experiments often struggle to reach the full sensitivity and time-resolution that FELs can in principle enable. Here, we implement a setup which solves two common challenges in this type of spectroscopy using FELs: First, we achieve a high spectral resolution by using a spectrometer downstream of the sample instead of a monochromator upstream of the sample. Thus, the full FEL bandwidth contributes to the measurement at the same time, and the FEL pulse duration is not elongated by a monochromator. Second, the FEL beam is divided into identical copies by a transmission grating beam splitter so that two spectra from separate spots on the sample (or from the sample and known reference) can be recorded in-parallel with the same spectrometer, enabling a spectrally resolved intensity normalization of pulse fluctuations in pump–probe scenarios. We analyze the capabilities of this setup around the oxygen K- and nickel L-edges recorded with third harmonic radiation of the free electron laser in Hamburg (FLASH), demonstrating the capability for pump–probe measurements with sensitivity to reflectivity changes on the per mill level.
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Dziarzhytski S, Biednov M, Dicke B, Wang A, Miedema PS, Engel RY, Schunck JO, Redlin H, Weigelt H, Siewert F, Behrens C, Sinha M, Schulte A, Grimm-Lebsanft B, Chiuzbăian SG, Wurth W, Beye M, Rübhausen M, Brenner G. The TRIXS end-station for femtosecond time-resolved resonant inelastic x-ray scattering experiments at the soft x-ray free-electron laser FLASH. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2020; 7:054301. [PMID: 32953941 PMCID: PMC7498279 DOI: 10.1063/4.0000029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 08/25/2020] [Indexed: 06/11/2023]
Abstract
We present the experimental end-station TRIXS dedicated to time-resolved soft x-ray resonant inelastic x-ray scattering (RIXS) experiments on solid samples at the free-electron laser FLASH. Using monochromatized ultrashort femtosecond XUV/soft x-ray photon pulses in combination with a synchronized optical laser in a pump-probe scheme, the TRIXS setup allows measuring sub-picosecond time-resolved high-resolution RIXS spectra in the energy range from 35 eV to 210 eV, thus spanning the M-edge (M1 and M2,3) absorption resonances of 3d transition metals and N4,5-edges of rare earth elements. A Kirkpatrick-Baez refocusing mirror system at the first branch of the plane grating monochromator beamline (PG1) provides a focus of (6 × 6) μm2 (FWHM) at the sample. The RIXS spectrometer reaches an energy resolution of 35-160 meV over the entire spectral range. The optical laser system based on a chirped pulse optical parametric amplifier provides approximately 100 fs (FWHM) long photon pulses at the fundamental wavelength of 800 nm and a fluence of 120 mJ/cm2 at a sample for optical pump-XUV probe measurements. Furthermore, optical frequency conversion enables experiments at 400 nm or 267 nm with a fluence of 80 and 30 mJ/cm2, respectively. Some of the first (pump-probe) RIXS spectra measured with this setup are shown. The measured time resolution for time-resolved RIXS measurements has been characterized as 287 fs (FWHM) for the used energy resolution.
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Affiliation(s)
| | - M. Biednov
- European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
| | - B. Dicke
- Institute of Nanostructure and Solid State Physics, University of Hamburg and Center for Free-Electron Laser Science (CFEL), Notkestr. 85, Hamburg 22607, Germany
| | - A. Wang
- Sorbonne Université, CNRS (UMR 7614), Laboratoire de Chimie Physique-Matière et Rayonnement, 4 Place Jussieu, 75252 Paris Cedex 05, France
| | | | | | | | - H. Redlin
- DESY, Notkestr. 85, Hamburg 22607, Germany
| | - H. Weigelt
- DESY, Notkestr. 85, Hamburg 22607, Germany
| | - F. Siewert
- Helmholtz Zentrum Berlin, Department Optics and Beamlines, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - C. Behrens
- DESY, Notkestr. 85, Hamburg 22607, Germany
| | - M. Sinha
- DESY, Notkestr. 85, Hamburg 22607, Germany
| | - A. Schulte
- DESY, Notkestr. 85, Hamburg 22607, Germany
| | - B. Grimm-Lebsanft
- Institute of Nanostructure and Solid State Physics, University of Hamburg and Center for Free-Electron Laser Science (CFEL), Notkestr. 85, Hamburg 22607, Germany
| | - S. G. Chiuzbăian
- Sorbonne Université, CNRS (UMR 7614), Laboratoire de Chimie Physique-Matière et Rayonnement, 4 Place Jussieu, 75252 Paris Cedex 05, France
| | - W. Wurth
- DESY, Notkestr. 85, Hamburg 22607, Germany
| | - M. Beye
- DESY, Notkestr. 85, Hamburg 22607, Germany
| | - M. Rübhausen
- Institute of Nanostructure and Solid State Physics, University of Hamburg and Center for Free-Electron Laser Science (CFEL), Notkestr. 85, Hamburg 22607, Germany
| | - G. Brenner
- DESY, Notkestr. 85, Hamburg 22607, Germany
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