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 - Eckert, Sebastian A1 - Miedema, P. S. A1 - Quevedo, W. A1 - Fondell, Mattis A1 - Beye, Martin A1 - Pietzsch, Annette A1 - Ross, M. A1 - Khalil, M. A1 - Föhlisch, Alexander T1 - Molecular structures and protonation state of 2-Mercaptopyridine in aqueous solution JF - Chemical physics letters N2 - The speciation of 2-Mercaptopyridine in aqueous solution has been investigated with nitrogen 1s Near Edge X-ray Absorption Fine Structure spectroscopy and time dependent Density Functional Theory. The prevalence of distinct species as a function of the solvent basicity is established. No indications of dimerization towards high concentrations are found. The determination of different molecular structures of 2-Mercaptopyridine in aqueous solution is put into the context of proton-transfer in keto-enol and thione-thiol tautomerisms. (C) 2016 The Authors. Published by Elsevier B.V. Y1 - 2016 U6 - https://doi.org/10.1016/j.cplett.2016.01.050 SN - 0009-2614 SN - 1873-4448 VL - 647 SP - 103 EP - 106 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Josefsson, I. A1 - Schreck, Simon Frederik A1 - Quevedo, W. A1 - Miedema, P. S. A1 - Techert, S. A1 - de Groot, F. M. F. A1 - Föhlisch, Alexander A1 - Odelius, M. A1 - Wernet, Ph. T1 - Quantifying covalent interactions with resonant inelastic soft X-ray scattering BT - case study of Ni2+ aqua complex JF - Chemical physics letters N2 - We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L-3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. We propose that 2p3d RIXS at the Ni L-3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations. KW - Transition-metal ion KW - Aqueous solution KW - Covalent interaction KW - Resonant inelastic X-ray scattering KW - Ligand-field state KW - Charge-transfer state Y1 - 2016 U6 - https://doi.org/10.1016/j.cplett.2016.12.046 SN - 0009-2614 SN - 1873-4448 VL - 669 SP - 196 EP - 201 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wernet, Philippe A1 - Leitner, T. A1 - Josefsson, Ida A1 - Mazza, T. A1 - Miedema, P. S. A1 - Schroder, H. A1 - Beye, Martin A1 - Kunnus, K. A1 - Schreck, S. A1 - Radcliffe, P. A1 - Dusterer, S. A1 - Meyer, M. A1 - Odelius, Michael A1 - Fohlisch, Alexander T1 - Communication: Direct evidence for sequential dissociation of gas-phase Fe(CO)(5) via a singlet pathway upon excitation at 266 nm JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - 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. Y1 - 2017 U6 - https://doi.org/10.1063/1.4984774 SN - 0021-9606 SN - 1089-7690 VL - 146 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Miedema, P. S. A1 - Mitzner, Rolf A1 - Ganschow, S. A1 - Föhlisch, Alexander A1 - Beye, Martin T1 - X-ray spectroscopy on the active ion in laser crystals JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - The active ions in typical laser crystals were studied with Resonant Inelastic X-ray Scattering (RIXS) and Partial Fluorescence Yield X-ray Absorption (PFY-XAS) spectroscopies as solid state model systems for dilute active centers. We analyzed Ti3+ and Cr3+ in alpha-Al2O3:Ti3+ and LiCaAlF6:Cr3+, respectively. The comparison of experimental data with semi-empirical multiplet calculations provides insights into the electronic structure and shows how measured crystal field energies are related across different spectroscopies. Y1 - 2017 U6 - https://doi.org/10.1039/c7cp03026f SN - 1463-9076 SN - 1463-9084 VL - 19 SP - 21800 EP - 21806 PB - Royal Society of Chemistry CY - Cambridge ER -