@article{KunnusJosefssonSchrecketal.2017, author = {Kunnus, Kristjan and Josefsson, I. and Schreck, Simon Frederik and Quevedo, W. and Miedema, P. S. and Techert, S. and de Groot, F. M. F. and F{\"o}hlisch, Alexander and Odelius, M. and Wernet, Ph.}, title = {Quantifying covalent interactions with resonant inelastic soft X-ray scattering}, series = {Chemical physics letters}, volume = {669}, journal = {Chemical physics letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0009-2614}, doi = {10.1016/j.cplett.2016.12.046}, pages = {196 -- 201}, year = {2017}, abstract = {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.}, language = {en} } @article{NiskanenJankalaHuttulaetal.2017, author = {Niskanen, Johannes and Jankala, Kari and Huttula, Marco and F{\"o}hlisch, Alexander}, title = {QED effects in 1s and 2s single and double ionization potentials of the noble gases}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {146}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4979991}, pages = {1443 -- 1450}, year = {2017}, abstract = {We present calculations on the quantum electrodynamics (QED) effects in 1s and 2s single and double ionization potentials of noble gases from Ne to Rn as perturbations on relativistic four-component Dirac-Fock wavefunctions. The most dominant effect originates from the self-energy of the core-electron that yields corrections of similar order as the transverse interaction. For 1s ionization potentials, a match within few eV against the known experimental values is obtained, and our work reveals considerable QED effects in the photoelectron binding energies across the periodic table-most strikingly even for Ne. We perform power-law fits for the corrections as a function of Z and interpolate the QED correction of similar to-0.55 eV for S1s. Due to this, the K-edge electron spectra of the third row and below need QED for a match in the absolute energy when using state-of-the-art instrumentation. Published by AIP Publishing.}, language = {en} } @article{NiskanenSahleGilmoreetal.2017, author = {Niskanen, Johannes and Sahle, Christoph J. and Gilmore, Keith and Uhlig, Frank and Smiatek, Jens and F{\"o}hlisch, Alexander}, title = {Disentangling structural information from core-level excitation spectra}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {96}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, publisher = {American Physical Society}, address = {College Park}, issn = {2470-0045}, doi = {10.1103/PhysRevE.96.013319}, pages = {8}, year = {2017}, abstract = {Core-level spectra of liquids can be difficult to interpret due to the presence of a range of local environments. We present computational methods for investigating core-level spectra based on the idea that both local structural parameters and the x-ray spectra behave as functions of the local atomic configuration around the absorbing site. We identify correlations between structural parameters and spectral intensities in defined regions of interest, using the oxygen K-edge excitation spectrum of liquid water as a test case. Our results show that this kind of analysis can find the main structure-spectral relationships of ice, liquid water, and supercritical water.}, language = {en} } @article{KubinKernGuletal.2017, author = {Kubin, Markus and Kern, Jan and Gul, Sheraz and Kroll, Thomas and Chatterjee, Ruchira and Loechel, Heike and Fuller, Franklin D. and Sierra, Raymond G. and Quevedo, Wilson and Weniger, Christian and Rehanek, Jens and Firsov, Anatoly and Laksmono, Hartawan and Weninger, Clemens and Alonso-Mori, Roberto and Nordlund, Dennis L. and Lassalle-Kaiser, Benedikt and Glownia, James M. and Krzywinski, Jacek and Moeller, Stefan and Turner, Joshua J. and Minitti, Michael P. and Dakovski, Georgi L. and Koroidov, Sergey and Kawde, Anurag and Kanady, Jacob S. and Tsui, Emily Y. and Suseno, Sandy and Han, Zhiji and Hill, Ethan and Taguchi, Taketo and Borovik, Andrew S. and Agapie, Theodor and Messinger, Johannes and Erko, Alexei and F{\"o}hlisch, Alexander and Bergmann, Uwe and Mitzner, Rolf and Yachandra, Vittal K. and Yano, Junko and Wernet, Philippe}, title = {Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers}, series = {Structural dynamics}, volume = {4}, journal = {Structural dynamics}, publisher = {American Institute of Physics}, address = {Melville}, issn = {2329-7778}, doi = {10.1063/1.4986627}, pages = {16}, year = {2017}, abstract = {X-ray absorption spectroscopy at the L-edge of 3d transition metals provides unique information on the local metal charge and spin states by directly probing 3d-derived molecular orbitals through 2p-3d transitions. However, this soft x-ray technique has been rarely used at synchrotron facilities for mechanistic studies of metalloenzymes due to the difficulties of x-ray-induced sample damage and strong background signals from light elements that can dominate the low metal signal. Here, we combine femtosecond soft x-ray pulses from a free-electron laser with a novel x-ray fluorescence-yield spectrometer to overcome these difficulties. We present L-edge absorption spectra of inorganic high-valent Mn complexes (Mn similar to 6-15 mmol/l) with no visible effects of radiation damage. We also present the first L-edge absorption spectra of the oxygen evolving complex (Mn4CaO5) in Photosystem II (Mn < 1 mmol/l) at room temperature, measured under similar conditions. Our approach opens new ways to study metalloenzymes under functional conditions. (C) 2017 Author(s).}, language = {en} } @article{YinInhesterVeeduetal.2017, author = {Yin, Zhong and Inhester, Ludger and Veedu, Sreevidya Thekku and Quevedo, Wilson and Pietzsch, Annette and Wernet, Philippe and Groenhof, Gerrit and F{\"o}hlisch, Alexander and Grubmueller, Helmut and Techert, Simone}, title = {Cationic and Anionic Impact on the Electronic Structure of Liquid Water}, series = {The journal of physical chemistry letters}, volume = {8}, journal = {The journal of physical chemistry letters}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.7b01392}, pages = {3759 -- 3764}, year = {2017}, abstract = {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.}, language = {en} } @article{ThielemannKuehnSchickPontiusetal.2017, author = {Thielemann-K{\"u}hn, Nele and Schick, Daniel and Pontius, Niko and Trabant, Christoph and Mitzner, Rolf and Holldack, Karsten and Zabel, Hartmut and F{\"o}hlisch, Alexander and Schuessler-Langeheine, Christian}, title = {Ultrafast and Energy-Efficient Quenching of Spin Order: Antiferromagnetism Beats Ferromagnetism}, series = {Physical review letters}, volume = {119}, journal = {Physical review letters}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.119.197202}, pages = {6}, year = {2017}, abstract = {By comparing femtosecond laser pulse induced ferro- and antiferromagnetic dynamics in one and the same material-metallic dysprosium-we show both to behave fundamentally different. Antiferromagnetic order is considerably faster and much more efficiently reduced by optical excitation than its ferromagnetic counterpart. We assign the fast and extremely efficient process in the antiferromagnet to an interatomic transfer of angular momentum within the spin system. Our findings imply that this angular momentum transfer channel is effective in other magnetic metals with nonparallel spin alignment. They also point out a possible route towards energy-efficient spin manipulation for magnetic devices.}, language = {en} } @article{MiedemaMitznerGanschowetal.2017, author = {Miedema, P. S. and Mitzner, Rolf and Ganschow, S. and F{\"o}hlisch, Alexander and Beye, Martin}, title = {X-ray spectroscopy on the active ion in laser crystals}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {19}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c7cp03026f}, pages = {21800 -- 21806}, year = {2017}, abstract = {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.}, language = {en} } @article{EckertNorellMiedemaetal.2017, author = {Eckert, Sebastian and Norell, Jesper and Miedema, Piter S. and Beye, Martin and Fondell, Mattis and Quevedo, Wilson and Kennedy, Brian and Hantschmann, Markus and Pietzsch, Annette and Van Kuiken, Benjamin E. and Ross, Matthew and Minitti, Michael P. and Moeller, Stefan P. and Schlotter, William F. and Khalil, Munira and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Ultrafast Independent N-H and N-C Bond Deformation Investigated with Resonant Inelastic X-Ray Scattering}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {56}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201700239}, pages = {6088 -- 6092}, year = {2017}, abstract = {The femtosecond excited-state dynamics following resonant photoexcitation enable the selective deformation of N-H and N-C chemical bonds in 2-thiopyridone in aqueous solution with optical or X-ray pulses. In combination with multiconfigurational quantum-chemical calculations, the orbital-specific electronic structure and its ultrafast dynamics accessed with resonant inelastic X-ray scattering at the N 1s level using synchrotron radiation and the soft X-ray free-electron laser LCLS provide direct evidence for this controlled photoinduced molecular deformation and its ultrashort time-scale.}, language = {en} } @article{VazdaCruzErtanCoutoetal.2017, author = {Vaz da Cruz, Vinicius and Ertan, Emelie and Couto, Rafael C. and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Guimaraes, Freddy F. and {\AA}gren, Hans and Odelius, Michael and F{\"o}hlisch, Alexander and Kimberg, Victor}, title = {A study of the water molecule using frequency control over nuclear dynamics in resonant X-ray scattering}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {19}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c7cp01215b}, pages = {19573 -- 19589}, year = {2017}, abstract = {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.}, language = {en} } @article{EckertNiskanenJayetal.2017, author = {Eckert, Sebastian and Niskanen, Johannes and Jay, Raphael Martin and Miedema, Piter S. and Fondell, Mattis and Kennedy, Brian and Quevedo, Wilson and Iannuzzi, Marcella and F{\"o}hlisch, Alexander}, title = {Valence orbitals and local bond dynamics around N atoms of histidine under X-ray irradiation}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {19}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c7cp05713j}, pages = {32091 -- 32098}, year = {2017}, abstract = {The valence orbitals of aqueous histidine under basic, neutral and acidic conditions and their X-ray induced transformations have been monitored through N 1s resonant inelastic X-ray scattering. Using density functional ab initio molecular dynamics simulations in the core-hole state within the Z + 1 approximation, core-excitation-induced molecular transformations are quantified. Spectroscopic evidence for a highly directional X-ray-induced local N-H dissociation within the scattering duration is presented for acidic histidine. Our report demonstrates a protonation-state and chemical-environment dependent propensity for a molecular dissociation, which is induced by the absorption of high energy photons. This case study indicates that structural deformations in biomolecules under exposure to ionizing radiation, yielding possible alteration or loss of function, is highly dependent on the physiological state of the molecule upon irradiation.}, language = {en} } @article{CoutoCruzErtanetal.2017, author = {Couto, Rafael C. and Cruz, Vinicius V. and Ertan, Emelie and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Guimaraes, Freddy F. and Agren, Hans and Odelius, Michael and Kimberg, Victor and F{\"o}hlisch, Alexander}, title = {Selective gating to vibrational modes through resonant X-ray scattering}, series = {Nature Communications}, volume = {8}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/ncomms14165}, pages = {7}, year = {2017}, abstract = {The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations.}, language = {en} } @article{CappelSvanstromLanzilottoetal.2017, author = {Cappel, Ute B. and Svanstrom, Sebastian and Lanzilotto, Valeria and Johansson, Fredrik O. L. and Aitola, Kerttu and Philippe, Bertrand and Giangrisostomi, Erika and Ovsyannikov, Ruslan and Leitner, Torsten and F{\"o}hlisch, Alexander and Svensson, Svante and Martensson, Nils and Boschloo, Gerrit and Lindblad, Andreas and Rensmo, Hakan}, title = {Partially Reversible Photoinduced Chemical Changes in a Mixed-Ion Perovskite Material for Solar Cells}, series = {ACS applied materials \& interfaces}, volume = {9}, journal = {ACS applied materials \& interfaces}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/acsami.7b10643}, pages = {34970 -- 34978}, year = {2017}, abstract = {Metal halide perovskites have emerged as materials of high interest for solar energy-to-electricity conversion, and in particular, the use of mixed-ion structures has led to high power conversion efficiencies and improved stability. For this reason, it is important to develop means to obtain atomic level understanding of the photoinduced behavior of these materials including processes such as photoinduced phase separation and ion migration. In this paper, we implement a new methodology combining visible laser illumination of a mixed-ion perovskite ((FAP-bI(3))(0.85)(MAPbBr(3))(0.15)) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites.}, language = {en} } @misc{CoutoCruzErtanetal.2017, author = {Couto, Rafael C. and Cruz, Vinicius V. and Ertan, Emelie and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Guimar{\~a}es, Freddy F. and {\AA}gren, Hans and Gel'mukhanov, Faris and Odelius, Michael and Kimberg, Victor and F{\"o}hlisch, Alexander}, title = {Selective gating to vibrational modes through resonant X-ray scattering}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1124}, issn = {1866-8372}, doi = {10.25932/publishup-43692}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436926}, pages = {9}, year = {2017}, abstract = {The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations.}, language = {en} } @misc{EckertNorellMiedemaetal.2017, author = {Eckert, Sebastian and Norell, Jesper and Miedema, Piter S. and Beye, Martin and Fondell, Mattis and Quevedo, Wilson and Kennedy, Brian and Hantschmann, Markus and Pietzsch, Annette and van Kuiken, Benjamin E. and Ross, Matthew and Minitti, Michael P. and Moeller, Stefan P. and Schlotter, William F. and Khalil, Munira and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Ultrafast Independent N-H and N-C Bond Deformation Investigated with Resonant Inelastic X-Ray Scattering}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1115}, issn = {1866-8372}, doi = {10.25932/publishup-43687}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436873}, pages = {7}, year = {2017}, abstract = {The femtosecond excited-state dynamics following resonant photoexcitation enable the selective deformation of N-H and N-C chemical bonds in 2-thiopyridone in aqueous solution with optical or X-ray pulses. In combination with multiconfigurational quantum-chemical calculations, the orbital-specific electronic structure and its ultrafast dynamics accessed with resonant inelastic X-ray scattering at the N 1s level using synchrotron radiation and the soft X-ray free-electron laser LCLS provide direct evidence for this controlled photoinduced molecular deformation and its ultrashort time-scale.}, language = {en} } @article{FondellEckertJayetal.2017, author = {Fondell, Mattis and Eckert, Sebastian and Jay, Raphael Martin and Weniger, Christian and Quevedo, Wilson and Niskanen, Johannes and Kennedy, Brian and Sorgenfrei, Nomi and Schick, Daniel and Giangrisostomi, Erika and Ovsyannikov, Ruslan and Adamczyk, Katrin and Huse, Nils and Wernet, Philippe and Mitzner, Rolf and F{\"o}hlisch, Alexander}, title = {Time-resolved soft X-ray absorption spectroscopy in transmission mode on liquids at MHz repetition rates}, series = {Structural dynamics}, volume = {4}, journal = {Structural dynamics}, publisher = {American Institute of Physics}, address = {Melville}, issn = {2329-7778}, doi = {10.1063/1.4993755}, pages = {11}, year = {2017}, abstract = {We present a setup combining a liquid flatjet sample delivery and a MHz laser system for time-resolved soft X-ray absorption measurements of liquid samples at the high brilliance undulator beamline UE52-SGM at Bessy II yielding unprecedented statistics in this spectral range. We demonstrate that the efficient detection of transient absorption changes in transmission mode enables the identification of photoexcited species in dilute samples. With iron(II)-trisbipyridine in aqueous solution as a benchmark system, we present absorption measurements at various edges in the soft X-ray regime. In combination with the wavelength tunability of the laser system, the set-up opens up opportunities to study the photochemistry of many systems at low concentrations, relevant to materials sciences, chemistry, and biology. (C) 2017 Author(s).}, language = {en} }