TY - JOUR A1 - Pietzsch, Annette A1 - Niskanen, Johannes A1 - Vaz da Cruz, Vinicius A1 - Büchner, Robby A1 - Eckert, Sebastian A1 - Fondell, Mattis A1 - Jay, Raphael Martin A1 - Lu, Xingye A1 - McNally, Daniel A1 - Schmitt, Thorsten A1 - Föhlisch, Alexander T1 - Cuts through the manifold of molecular H2O potential energy surfaces in liquid water at ambient conditions JF - Proceedings of the National Academy of Sciences of the United States of America N2 - The fluctuating hydrogen bridge bonded network of liquid water at ambient conditions entails a varied ensemble of the underlying constituting H2O molecular moieties. This is mirrored in a manifold of the H2O molecular potentials. Subnatural line width resonant inelastic X-ray scattering allowed us to quantify the manifold of molecular potential energy surfaces along the H2O symmetric normal mode and the local asymmetric O-H bond coordinate up to 1 and 1.5 angstrom, respectively. The comparison of the single H2O molecular potentials and spectroscopic signatures with the ambient conditions liquid phase H2O molecular potentials is done on various levels. In the gas phase, first principles, Morse potentials, and stepwise harmonic potential reconstruction have been employed and benchmarked. In the liquid phase the determination of the potential energy manifold along the local asymmetric O-H bond coordinate from resonant inelastic X-ray scattering via the bound state oxygen ls to 4a(1) resonance is treated within these frameworks. The potential energy surface manifold along the symmetric stretch from resonant inelastic X-ray scattering via the oxygen 1 s to 2b(2) resonance is based on stepwise harmonic reconstruction. We find in liquid water at ambient conditions H2O molecular potentials ranging from the weak interaction limit to strongly distorted potentials which are put into perspective to established parameters, i.e., intermolecular O-H, H-H, and O-O correlation lengths from neutron scattering. KW - water KW - potential ene rgy surface KW - RIXS Y1 - 2022 U6 - https://doi.org/10.1073/pnas.2118101119 SN - 1091-6490 VL - 119 IS - 28 PB - National Acad. of Sciences CY - Washington, DC ER - TY - JOUR A1 - Yin, Zhong A1 - Rajkovic, Ivan A1 - Veedu, Sreevidya Thekku A1 - Deinert, Sascha A1 - Raiser, Dirk A1 - Jain, Rohit A1 - Fukuzawa, Hironobu A1 - Wada, Shin-ichi A1 - Quevedo, Wilson A1 - Kennedy, Brian A1 - Schreck, Simon A1 - Pietzsch, Annette A1 - Wernet, Philippe A1 - Ueda, Kyoshi A1 - Föhlisch, Alexander A1 - Techert, Simone T1 - Ionic solutions probed by resonant inelastic X-ray scattering JF - Zeitschrift für physikalische Chemie : international journal of research in physical chemistry and chemical physics N2 - 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. KW - X-ray Spectroscopy KW - XAS KW - XES KW - RIXS KW - Anions KW - Cations KW - Liquid Jet KW - Synchrotron Radiation Y1 - 2015 U6 - https://doi.org/10.1515/zpch-2015-0610 SN - 0942-9352 VL - 229 IS - 10-12 SP - 1855 EP - 1867 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Schreck, Simon A1 - Föhlisch, Alexander T1 - Free-electron laser based resonant inelastic X-ray scattering on molecules and liquids JF - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy N2 - The unprecedented beam properties of free-electron laser based X-ray sources enable novel resonant inelastic X-ray scattering (RIXS) experiments. Femtosecond time-resolved RIXS can be used to follow charge, spin and structural dynamics of dilute solute molecules in solution. Ultrashort X-ray pulses allow probing of highly radiation sensitive states of matter such as the metastable phase of supercooled liquid water. Nonlinear X-ray probes like amplified spontaneous emission and stimulated resonant X-ray scattering provide an enhanced selectivity and sensitivity as well as a path to control radiation damage and increase the photon yields in RIXS experiments. (C) 2015 Elsevier B.V. All rights reserved. KW - Free-electron laser KW - RIXS KW - Pump-probe KW - Nonlinear X-ray spectroscopy KW - Molecules KW - Liquids Y1 - 2015 U6 - https://doi.org/10.1016/j.elspec.2015.08.012 SN - 0368-2048 SN - 1873-2526 VL - 204 SP - 345 EP - 355 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Miedema, P. S. A1 - Beye, Martin A1 - Koennecke, R. A1 - Schiwietz, G. A1 - Föhlisch, Alexander T1 - The angular- and crystal-momentum transfer through electron-phonon coupling in silicon and silicon-carbide: similarities and differences JF - New journal of physics : the open-access journal for physics N2 - Electron-phonon scattering has been studied for silicon carbide (6H-SiC) with resonant inelastic x-ray scattering at the silicon 2p edge. The observed electron-phonon scattering yields a crystal momentum transfer rate per average phonon in 6H-SiC of 1.8 fs(-1) while it is 0.2 fs(-1) in crystalline silicon. The angular momentum transfer rate per average phonon for 6H-SiC is 0.1 fs(-1), which is much higher than 0.0035 fs(-1) obtained for crystalline silicon in a previous study. The higher electron-phonon scattering rates in 6H-SiC are a result of the larger electron localization at the silicon atoms in 6H-SiC as compared to crystalline silicon. While delocalized valence electrons can screen effectively (part of) the electron-phonon interaction, this effect is suppressed for 6H-SiC in comparison to crystalline silicon. Smaller contributions to the difference in electron-phonon scattering rates between 6H-SiC and silicon arise from the lower atomic mass of carbon versus silicon and the difference in local symmetry. KW - electron-phonon scattering KW - 6H-SiC KW - RIXS Y1 - 2014 U6 - https://doi.org/10.1088/1367-2630/16/9/093056 SN - 1367-2630 VL - 16 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Miedema, Piter Sybren A1 - Beye, Martin A1 - Koennecke, R. A1 - Schiwietz, Gregor A1 - Föhlisch, Alexander T1 - Thermal evolution of the band edges of 6H-SiC: X-ray methods compared to the optical band gap JF - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy N2 - The band gap of semiconductors like silicon and silicon carbide (SIC) is the key for their device properties. In this research, the band gap of 6H-SiC and its temperature dependence were analyzed with silicon 2p X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) allowing for a separate analysis of the conduction-band minimum (CBM) and valence-band maximum (VBM) components of the band gap. The temperature-dependent asymmetric band gap shrinking of 6H-SiC was determined with a valence-band slope of +2.45 x 10(-4) eV/K and a conduction-band slope of -1.334 x 10(-4) eV/K. The apparent asymmetry, e.g., that two thirds of the band-gap shrinking with increasing temperature is due to the VBM evolution in 6H-SiC, is similar to the asymmetry obtained for pure silicon before. The overall band gap temperature-dependence determined with XAS and nonresonant XES is compared to temperature-dependent optical studies. The core-excitonic binding energy appearing in the Si 2p XAS is extracted as the main difference. In addition, the energy loss of the onset of the first band in RIXS yields to values similar to the optical band gap over the tested temperature range. (C) 2014 Elsevier B.V. All rights reserved. KW - RIXS KW - XAS KW - XES KW - Semiconductors KW - Silicon carbide Y1 - 2014 U6 - https://doi.org/10.1016/j.elspec.2014.08.003 SN - 0368-2048 SN - 1873-2526 VL - 197 SP - 37 EP - 42 PB - Elsevier CY - Amsterdam ER -