@article{BeitzBechmannMitzner1998, author = {Beitz, Toralf and Bechmann, Wolfgang and Mitzner, Rolf}, title = {Investigations of reactions of selected Azaarenes with radicals in water, 2. Chlorine and Bromine radicals}, year = {1998}, language = {en} } @article{BeitzBechmannMitzner1998, author = {Beitz, Toralf and Bechmann, Wolfgang and Mitzner, Rolf}, title = {Investigations of reactions of selected Azaarenes with radicals in water, 1. Hydroxyl and sulfate radicals}, year = {1998}, language = {en} } @article{BeitzBechmannMitzner1999, author = {Beitz, Toralf and Bechmann, Wolfgang and Mitzner, Rolf}, title = {Investigation on the photoreactions of Nitrate and Nitrite ions with selected Azaarenes in water}, year = {1999}, language = {en} } @article{EckertMascarenhasMitzneretal.2022, author = {Eckert, Sebastian and Mascarenhas, Eric Johnn and Mitzner, Rolf and Jay, Raphael Martin and Pietzsch, Annette and Fondell, Mattis and Vaz da Cruz, Vinicius and F{\"o}hlisch, Alexander}, title = {From the free ligand to the transition metal complex}, series = {Inorganic chemistry}, volume = {61}, journal = {Inorganic chemistry}, number = {27}, publisher = {American Chemical Society}, address = {Washington}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.2c00789}, pages = {10321 -- 10328}, year = {2022}, abstract = {Chelating agents are an integral part of transition metal complex chemistry with broad biological and industrial relevance. The hexadentate chelating agent ethylenediaminetetraacetic acid (EDTA) has the capability to bind to metal ions at its two nitrogen and four of its carboxylate oxygen sites. We use resonant inelastic X-ray scattering at the 1s absorption edge of the aforementioned elements in EDTA and the iron(III)-EDTA complex to investigate the impact of the metal-ligand bond formation on the electronic structure of EDTA. Frontier orbital distortions, occupation changes, and energy shifts through metal- ligand bond formation are probed through distinct spectroscopic signatures.}, language = {en} } @article{EckertNorellJayetal.2019, author = {Eckert, Sebastian and Norell, Jesper and Jay, Raphael Martin and Fondell, Mattis and Mitzner, Rolf and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {T-1 Population as the Driver of Excited-State Proton-Transfer in 2-Thiopyridone}, series = {Chemistry - a European journal}, volume = {25}, journal = {Chemistry - a European journal}, number = {7}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201804166}, pages = {1733 -- 1739}, year = {2019}, abstract = {Excited-state proton transfer (ESPT) is a fundamental process in biomolecular photochemistry, but its underlying mediators often evade direct observation. We identify a distinct pathway for ESPT in aqueous 2-thiopyridone, by employing transient N1s X-ray absorption spectroscopy and multi-configurational spectrum simulations. Photoexcitations to the singlet S-2 and S-4 states both relax promptly through intersystem crossing to the triplet T-1 state. The T-1 state, through its rapid population and near nanosecond lifetime, mediates nitrogen site deprotonation by ESPT in a secondary intersystem crossing to the S-0 potential energy surface. This conclusively establishes a dominant ESPT pathway for the system in aqueous solution, which is also compatible with previous measurements in acetonitrile. Thereby, the hitherto open questions of the pathway for ESPT in the compound, including its possible dependence on excitation wavelength and choice of solvent, are resolved.}, language = {en} } @article{EschenlohrBattiatoMaldonadoetal.2013, author = {Eschenlohr, Andrea and Battiato, Marco and Maldonado, R. and Pontius, N. and Kachel, T. and Holldack, K. and Mitzner, Rolf and F{\"o}hlisch, Alexander and Oppeneer, P. M. and Stamm, C.}, title = {Ultrafast spin transport as key to femtosecond demagnetization}, series = {Nature materials}, volume = {12}, journal = {Nature materials}, number = {4}, publisher = {Nature Publ. Group}, address = {London}, issn = {1476-1122}, doi = {10.1038/NMAT3546}, pages = {332 -- 336}, year = {2013}, abstract = {Irradiating a ferromagnet with a femtosecond laser pulse is known to induce an ultrafast demagnetization within a few hundred femtoseconds. Here we demonstrate that direct laser irradiation is in fact not essential for ultrafast demagnetization, and that electron cascades caused by hot electron currents accomplish it very efficiently. We optically excite a Au/Ni layered structure in which the 30 nm Au capping layer absorbs the incident laser pump pulse and subsequently use the X-ray magnetic circular dichroism technique to probe the femtosecond demagnetization of the adjacent 15 nm Ni layer. A demagnetization effect corresponding to the scenario in which the laser directly excites the Ni film is observed, but with a slight temporal delay. We explain this unexpected observation by means of the demagnetizing effect of a superdiffusive current of non-equilibrium, non-spin-polarized electrons generated in the Au layer.}, language = {en} } @misc{EschenlohrBattiatoMaldonadoetal.2014, author = {Eschenlohr, Andrea and Battiato, Mario and Maldonado, P. and Pontius, N. and Kachel, T. and Holldack, K. and Mitzner, Rolf and F{\"o}hlisch, Alexander and Oppeneer, P. M. and Stamm, Christian}, title = {Optical excitation of thin magnetic layers in multilayer structures Reply}, series = {Nature materials}, volume = {13}, journal = {Nature materials}, number = {2}, publisher = {Nature Publ. Group}, address = {London}, issn = {1476-1122}, doi = {10.1038/nmat3851}, pages = {102 -- 103}, year = {2014}, language = {en} } @misc{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 = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {780}, issn = {1866-8372}, doi = {10.25932/publishup-43752}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-437529}, pages = {12}, 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.}, 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} } @article{GiangrisostomiOvsyannikovSorgenfreietal.2018, author = {Giangrisostomi, Erika and Ovsyannikov, Ruslan and Sorgenfrei, Nomi and Zhang, Teng and Lindblad, Andreas and Sassa, Yasmine and Cappel, Ute B. and Leitner, Torsten and Mitzner, Rolf and Svensson, Svante and Martensson, Nils and F{\"o}hlisch, Alexander}, title = {Low Dose Photoelectron Spectroscopy at BESSY II}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {224}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0368-2048}, doi = {10.1016/j.elspec.2017.05.011}, pages = {68 -- 78}, year = {2018}, abstract = {The implementation of a high-transmission, angular-resolved time-of-Right electron spectrometer with a 1.25 MHz pulse selector at the PM4 soft X-ray dipole beamline of the synchrotron BESSY II creates unique capabilities to inquire electronic structure via photoelectron spectroscopy with a minimum of radiation dose. Solid-state samples can be prepared and characterized with standard UHV techniques and rapidly transferred from various preparation chambers to a 4-axis temperature-controlled measurement stage. A synchronized MHz laser system enables excited-state characterization and dynamical studies starting from the picosecond timescale. This article introduces the principal characteristics of the PM4 beamline and LowDosePES end-station. Recent results from graphene, an organic hole transport material for solar cells and the transition metal dichalcogenide MoS2 are presented to demonstrate the instrument performances.}, language = {en} } @article{JayEckertMitzneretal.2020, author = {Jay, Raphael M. and Eckert, Sebastian and Mitzner, Rolf and Fondell, Mattis and F{\"o}hlisch, Alexander}, title = {Quantitative evaluation of transient valence orbital occupations in a 3d transition metal complex as seen from the metal and ligand perspective}, series = {Chemical physics letters}, volume = {754}, journal = {Chemical physics letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0009-2614}, doi = {10.1016/j.cplett.2020.137681}, pages = {5}, year = {2020}, abstract = {It is demonstrated for the case of photo-excited ferrocyanide how time-resolved soft X-ray absorption spectroscopy in transmission geometry at the ligand K-edge and metal L-3-edge provides quantitatively equivalent valence electronic structure information, where signatures of photo-oxidation are assessed locally at the metal as well as the ligand. This allows for a direct and independent quantification of the number of photo-oxidized molecules at two soft X-ray absorption edges highlighting the sensitivity of X-ray absorption spectroscopy to the valence orbital occupation of 3d transition metal complexes throughout the soft X-ray range.}, language = {en} } @article{JayVazdaCruzEckertetal.2020, author = {Jay, Raphael M. and Vaz da Cruz, Vinicius and Eckert, Sebastian and Fondell, Mattis and Mitzner, Rolf and F{\"o}hlisch, Alexander}, title = {Probing solute-solvent interactions of transition metal complexes using L-edge absorption spectroscopy}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {124}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {27}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/acs.jpcb.0c00638}, pages = {5636 -- 5645}, year = {2020}, abstract = {In order to tailor solution-phase chemical reactions involving transition metal complexes, it is critical to understand how their valence electronic charge distributions are affected by the solution environment. Here, solute-solvent interactions of a solvatochromic mixed-ligand iron complex were investigated using X-ray absorption spectroscopy at the transition metal L-2,L-3-edge. Due to the selectivity of the corresponding core excitations to the iron 3d orbitals, the method grants direct access to the valence electronic structure around the iron center and its response to interactions with the solvent environment. A linear increase of the total L-2,L-3-edge absorption cross section as a function of the solvent Lewis acidity is revealed. The effect is caused by relative changes in different metal-ligand-bonding channels, which preserve local charge densities while increasing the density of unoccupied states around the iron center. These conclusions are corroborated by a combination of molecular dynamics and spectrum simulations based on time-dependent density functional theory. The simulations reproduce the spectral trends observed in the X-ray but also optical absorption experiments. Our results underscore the importance of solute-solvent interactions when aiming for an accurate description of the valence electronic structure of solvated transition metal complexes and demonstrate how L-2,L-3-edge absorption spectroscopy can aid in understanding the impact of the solution environment on intramolecular covalency and the electronic charge distribution.}, language = {en} } @article{JayEckertVazdaCruzetal.2019, author = {Jay, Raphael Martin and Eckert, Sebastian and Vaz da Cruz, Vinicius and Fondell, Mattis and Mitzner, Rolf and F{\"o}hlisch, Alexander}, title = {Covalency-driven preservation of local charge densities in a metal-to-ligand charge-transfer excited iron photosensitizer}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {58}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, number = {31}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201904761}, pages = {10742 -- 10746}, year = {2019}, abstract = {Charge-density rearrangements after metal-to-ligand charge-transfer excitation in an iron photosensitizer are investigated by R. M Jay, A. Fohlisch et al. in their Communication (DOI: 10.1002/anie.201904761). By using time-resolved X-ray absorption spectroscopy, surprising covalency-effects are revealed that inhibit charge-separation at the intra-molecular level. Furthermore, the underlying mechanism is proposed to be generally in effect for all commonly used photosensitizers in light-harvesting applications, which challenges the common perception of electronic charge-transfer.}, language = {en} } @article{KalliesKochMitzner1997, author = {Kallies, Bernd and Koch, Andreas and Mitzner, Rolf}, title = {Competitive resonance at the carbonyl group as visualized by the natural bond orbital analysis}, year = {1997}, language = {en} } @article{KalliesMitzner1998, author = {Kallies, Bernd and Mitzner, Rolf}, title = {Models of water-assisted hydrolyses of methyl formate, formamide, and urea from combined DFT-SCRF calculations}, year = {1998}, abstract = {In this work we present theoretical studies of the hydrolytic reaction of methyl formate, formamide and urea with one water molecule. The studied systems contain two additional water molecules which can act as bifunctional acid- base catalysts. These water molecules catalyze proton transfers between the primary reacting species. Our models describe the concerted transfer of two protons in every reaction step. The calculations have been carried out with the Becke3LYP/6-31G* method. Unspecific solvation effects have been included by means of a polarizable continuum model. Substrate reactivity differences as well as preferences for different reaction pathways can be discussed with the aid of these molecular systems. The studied alternative mechanisms include the common addition-elimination mechanism via a tetrahedral intermediate, and a concerted SN-like mechanism without a reaction intermediate. Our results suggest that the proved decreasing substrate reactivity in the order ester, amide, urea is caused by a rising resonance stabilization of the reaction centre, and not by a different positive partial charge of the carbonyl carbon. It is also concluded, that the probability of a concerted addition of a nucleophile and elimination of a leaving group without a tetrahedral intermediate rises in the order ester, amide, urea. The ordering of reactivity is not influenced by this behaviour.}, language = {en} } @article{KalliesMitzner1998, author = {Kallies, Bernd and Mitzner, Rolf}, title = {Structural Properties of Protonated Acyl Derivatives as Studied by Quantum Mechanics}, year = {1998}, abstract = {Basicities of 16 acyl compounds including selected aldehydes, ketones, esters, amides and ureas in the gas phase and in water were calculated with the Becke3LYP/6-31G* method. Solvent effects were modeled using a polarizable electrostatic continuum representation of the solvent. The properties of the electron densities of protonated molecules were described by localized bond orbitals. Our results suggest that the carbonyl oxygen is the preferred site of protonation for all molecules studied. Calculated pKa values in water range from -12 for aldehydes to + 1.5 for ureas. They agree well with published experimental data. We found that a high basicity of acyl compounds at the carbonyl oxygen is coupled with a large amount of additional resonance stabilization at the carbonyl group. The protonation of the leaving group of eaters, amides and ureas is less preferred, but the basicity difference between C=O and -OR or -NR2 decreases from esters to ureas. Calculated pKa values for this site range from -18 for esters to + 3 for ureas. These values are often not accessible by experiment. The structure of carboxylic acid derivatives protonated at the leaving group is determined by prefragmentation of the molecules into an acylium ion or positively charged isocyanate and an alcohol or amine. (C) 1998 Elsevier Science B.V.}, language = {en} } @article{KrollKernKubinetal.2016, author = {Kroll, Thomas and Kern, Jan and Kubin, Markus and Ratner, Daniel and Gul, Sheraz and Fuller, Franklin D. and L{\"o}chel, Heike and Krzywinski, Jacek and Lutman, Alberto and Ding, Yuantao and Dakovski, Georgi L. and Moeller, Stefan and Turner, Joshua J. and Alonso-Mori, Roberto and Nordlund, Dennis L. and Rehanek, Jens and Weniger, Christian and Firsov, Alexander and Brzhezinskaya, Maria and Chatterjee, Ruchira and Lassalle-Kaiser, Benedikt and Sierra, Raymond G. and Laksmono, Hartawan and Hill, Ethan and Borovik, Andrew S. and Erko, Alexei and F{\"o}hlisch, Alexander and Mitzner, Rolf and Yachandra, Vittal K. and Yano, Junko and Wernet, Philippe and Bergmann, Uwe}, title = {X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser}, series = {Optics express : the international electronic journal of optics}, volume = {24}, journal = {Optics express : the international electronic journal of optics}, publisher = {Optical Society of America}, address = {Washington}, issn = {1094-4087}, doi = {10.1364/OE.24.022469}, pages = {22469 -- 22480}, year = {2016}, abstract = {X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. However, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. Here we compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. We show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements. (C) 2016 Optical Society of America}, language = {en} } @article{KubinGuoKrolletal.2018, author = {Kubin, Markus and Guo, Meiyuan and Kroll, Thomas and Loechel, Heike and Kallman, Erik and Baker, Michael L. and Mitzner, Rolf and Gul, Sheraz and Kern, Jan and F{\"o}hlisch, Alexander and Erko, Alexei and Bergmann, Uwe and Yachandra, Vittal and Yano, Junko and Lundberg, Marcus and Wernet, Philippe}, title = {Probing the oxidation state of transition metal complexes}, series = {Chemical science}, volume = {9}, journal = {Chemical science}, number = {33}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2041-6520}, doi = {10.1039/c8sc00550h}, pages = {6813 -- 6829}, year = {2018}, abstract = {Transition metals in inorganic systems and metalloproteins can occur in different oxidation states, which makes them ideal redox-active catalysts. To gain a mechanistic understanding of the catalytic reactions, knowledge of the oxidation state of the active metals, ideally in operando, is therefore critical. L-edge X-ray absorption spectroscopy (XAS) is a powerful technique that is frequently used to infer the oxidation state via a distinct blue shift of L-edge absorption energies with increasing oxidation state. A unified description accounting for quantum-chemical notions whereupon oxidation does not occur locally on the metal but on the whole molecule and the basic understanding that L-edge XAS probes the electronic structure locally at the metal has been missing to date. Here we quantify how charge and spin densities change at the metal and throughout the molecule for both redox and core-excitation processes. We explain the origin of the L-edge XAS shift between the high-spin complexes Mn-II(acac)(2) and Mn-III(acac)(3) as representative model systems and use ab initio theory to uncouple effects of oxidation-state changes from geometric effects. The shift reflects an increased electron affinity of Mn-III in the core-excited states compared to the ground state due to a contraction of the Mn 3d shell upon core-excitation with accompanied changes in the classical Coulomb interactions. This new picture quantifies how the metal-centered core hole probes changes in formal oxidation state and encloses and substantiates earlier explanations. The approach is broadly applicable to mechanistic studies of redox-catalytic reactions in molecular systems where charge and spin localization/delocalization determine reaction pathways.}, language = {en} } @misc{KubinGuoKrolletal.2018, author = {Kubin, Markus and Guo, Meiyuan and Kroll, Thomas and L{\"o}chel, Heike and K{\"a}llman, Erik and Baker, Michael L. and Mitzner, Rolf and Gul, Sheraz and Kern, Jan and F{\"o}hlisch, Alexander and Erko, Alexei and Bergmann, Uwe and Yachandra, Vittal and Yano, Junko and Lundberg, Marcus and Wernet, Philippe}, title = {Probing the oxidation state of transition metal complexes}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {656}, issn = {1866-8372}, doi = {10.25932/publishup-42505}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-425057}, pages = {17}, year = {2018}, abstract = {Transition metals in inorganic systems and metalloproteins can occur in different oxidation states, which makes them ideal redox-active catalysts. To gain a mechanistic understanding of the catalytic reactions, knowledge of the oxidation state of the active metals, ideally in operando, is therefore critical. L-edge X-ray absorption spectroscopy (XAS) is a powerful technique that is frequently used to infer the oxidation state via a distinct blue shift of L-edge absorption energies with increasing oxidation state. A unified description accounting for quantum-chemical notions whereupon oxidation does not occur locally on the metal but on the whole molecule and the basic understanding that L-edge XAS probes the electronic structure locally at the metal has been missing to date. Here we quantify how charge and spin densities change at the metal and throughout the molecule for both redox and core-excitation processes. We explain the origin of the L-edge XAS shift between the high-spin complexes Mn-II(acac)(2) and Mn-III(acac)(3) as representative model systems and use ab initio theory to uncouple effects of oxidation-state changes from geometric effects. The shift reflects an increased electron affinity of Mn-III in the core-excited states compared to the ground state due to a contraction of the Mn 3d shell upon core-excitation with accompanied changes in the classical Coulomb interactions. This new picture quantifies how the metal-centered core hole probes changes in formal oxidation state and encloses and substantiates earlier explanations. The approach is broadly applicable to mechanistic studies of redox-catalytic reactions in molecular systems where charge and spin localization/delocalization determine reaction pathways.}, 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{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{MitznerRehanekKernetal.2013, author = {Mitzner, Rolf and Rehanek, Jens and Kern, Jan and Gul, Sheraz and Hattne, Johan and Taguchi, Taketo and Alonso-Mori, Roberto and Tran, Rosalie and Weniger, Christian and Schr{\"o}der, Henning and Quevedo, Wilson and Laksmono, Hartawan and Sierra, Raymond G. and Han, Guangye and Lassalle-Kaiser, Benedikt and Koroidov, Sergey and Kubicek, Katharina and Schreck, Simon and Kunnus, Kristjan and Brzhezinskaya, Maria and Firsov, Alexander and Minitti, Michael P. and Turner, Joshua J. and M{\"o}ller, Stefan and Sauter, Nicholas K. and Bogan, Michael J. and Nordlund, Dennis and Schlotter, William F. and Messinger, Johannes and Borovik, Andrew S. and Techert, Simone and de Groot, Frank M. F. and F{\"o}hlisch, Alexander and Erko, Alexei and Bergmann, Uwe and Yachandra, Vittal K. and Wernet, Philippe and Yano, Junko}, title = {L-edge x-ray absorption spectroscopy of dilute systems relevant to metalloproteins using an X-ray free-electron laser}, series = {The journal of physical chemistry letters}, volume = {4}, journal = {The journal of physical chemistry letters}, number = {21}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/jz401837f}, pages = {3641 -- 3647}, year = {2013}, abstract = {L-edge spectroscopy of 3d transition metals provides important electronic structure information and has been used in many fields. However, the use of this method for studying dilute aqueous systems, such as metalloenzymes, has not been prevalent because of severe radiation damage and the lack of suitable detection systems. Here we present spectra from a dilute Mn aqueous solution using a high-transmission zone-plate spectrometer at the Linac Coherent Light Source (LCLS). The spectrometer has been optimized for discriminating the Mn L-edge signal from the overwhelming 0 K-edge background that arises from water and protein itself, and the ultrashort LCLS X-ray pulses can outrun X-ray induced damage. We show that the deviations of the partial-fluorescence yield-detected spectra from the true absorption can be well modeled using the state-dependence of the fluorescence yield, and discuss implications for the application of our concept to biological samples.}, language = {en} } @article{PontiusBeyeTrabantetal.2018, author = {Pontius, Niko and Beye, Martin and Trabant, Christoph and Mitzner, Rolf and Sorgenfrei, Nomi and Kachel, Torsten and Woestmann, Michael and Roling, Sebastian and Zacharias, Helmut and Ivanov, Rosen and Treusch, Rolf and Buchholz, Marcel and Metcalf, Pete and Schuessler-Langeheine, Christian and F{\"o}hlisch, Alexander}, title = {Probing the non-equilibrium transient state in magnetite by a jitter-free two-color X-ray pump and X-ray probe experiment}, series = {Structural dynamics}, volume = {5}, journal = {Structural dynamics}, number = {5}, publisher = {American Institute of Physics}, address = {Melville}, issn = {2329-7778}, doi = {10.1063/1.5042847}, pages = {8}, year = {2018}, abstract = {We present a general experimental concept for jitter-free pump and probe experiments at free electron lasers. By generating pump and probe pulse from one and the same X-ray pulse using an optical split-and-delay unit, we obtain a temporal resolution that is limited only by the X-ray pulse lengths. In a two-color X-ray pump and X-ray probe experiment with sub 70 fs temporal resolution, we selectively probe the response of orbital and charge degree of freedom in the prototypical functional oxide magnetite after photoexcitation. We find electronic order to be quenched on a time scale of (30 +/- 30) fs and hence most likely faster than what is to be expected for any lattice dynamics. Our experimental result hints to the formation of a short lived transient state with decoupled electronic and lattice degree of freedom in magnetite. The excitation and relaxation mechanism for X-ray pumping is discussed within a simple model leading to the conclusion that within the first 10 fs the original photoexcitation decays into low-energy electronic excitations comparable to what is achieved by optical pump pulse excitation. Our findings show on which time scales dynamical decoupling of degrees of freedom in functional oxides can be expected and how to probe this selectively with soft X-ray pulses. Results can be expected to provide crucial information for theories for ultrafast behavior of materials and help to develop concepts for novel switching devices. (C) 2018 Author(s).}, language = {en} } @misc{SchickEckertPontiusetal.2016, author = {Schick, Daniel and Eckert, Sebastian and Pontius, Niko and Mitzner, Rolf and F{\"o}hlisch, Alexander and Holldack, Karsten and Sorgenfrei, Nomi}, title = {Versatile soft X-ray-optical cross-correlator for ultrafast applications}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1331}, issn = {1866-8372}, doi = {10.25932/publishup-43696}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436962}, pages = {054304-1 -- 054304-8}, year = {2016}, abstract = {We present an X-ray-optical cross-correlator for the soft (> 150 eV) up to the hard X-ray regime based on a molybdenum-silicon superlattice. The cross-correlation is done by probing intensity and position changes of superlattice Bragg peaks caused by photoexcitation of coherent phonons. This approach is applicable for a wide range of X-ray photon energies as well as for a broad range of excitation wavelengths and requires no external fields or changes of temperature. Moreover, the cross-correlator can be employed on a 10 ps or 100 fs time scale featuring up to 50\% total X-ray reflectivity and transient signal changes of more than 20\%. (C) 2016 Author(s).}, language = {en} } @article{SchickEckertPontiusetal.2016, author = {Schick, Daniel and Eckert, Sebastian and Pontius, Niko and Mitzner, Rolf and F{\"o}hlisch, Alexander and Holldack, Karsten and Sorgenfrei, Nomi}, title = {Versatile soft X-ray-optical cross-correlator for ultrafast applications}, series = {Structural dynamics}, volume = {3}, journal = {Structural dynamics}, publisher = {American Institute of Physics}, address = {Melville}, issn = {2329-7778}, doi = {10.1063/1.4964296}, pages = {054304-1 -- 054304-8}, year = {2016}, abstract = {We present an X-ray-optical cross-correlator for the soft (> 150 eV) up to the hard X-ray regime based on a molybdenum-silicon superlattice. The cross-correlation is done by probing intensity and position changes of superlattice Bragg peaks caused by photoexcitation of coherent phonons. This approach is applicable for a wide range of X-ray photon energies as well as for a broad range of excitation wavelengths and requires no external fields or changes of temperature. Moreover, the cross-correlator can be employed on a 10 ps or 100 fs time scale featuring up to 50\% total X-ray reflectivity and transient signal changes of more than 20\%. (C) 2016 Author(s).}, language = {en} } @article{SchickLeGuyaderPontiusetal.2016, author = {Schick, Daniel and Le Guyader, Loic and Pontius, Niko and Radu, Ilie and Kachel, Torsten and Mitzner, Rolf and Zeschke, Thomas and Schuessler-Langeheine, Christian and F{\"o}hlisch, Alexander and Holldack, Karsten}, title = {Analysis of the halo background in femtosecond slicing experiments}, series = {Journal of synchrotron radiation}, volume = {23}, journal = {Journal of synchrotron radiation}, publisher = {International Union of Crystallography}, address = {Chester}, issn = {1600-5775}, doi = {10.1107/S160057751600401X}, pages = {700 -- 711}, year = {2016}, abstract = {The slicing facility FemtoSpeX at BESSY II offers unique opportunities to study photo-induced dynamics on femtosecond time scales by means of X-ray magnetic circular dichroism, resonant and non-resonant X-ray diffraction, and X-ray absorption spectroscopy experiments in the soft X-ray regime. Besides femtosecond X-ray pulses, slicing sources inherently also produce a so-called `halo' background with a different time structure, polarization and pointing. Here a detailed experimental characterization of the halo radiation is presented, and a method is demonstrated for its correct and unambiguous removal from femtosecond time-resolved data using a special laser triggering scheme as well as analytical models. Examples are given for time-resolved measurements with corresponding halo correction, and errors of the relevant physical quantities caused by either neglecting or by applying a simplified model to describe this background are estimated.}, 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} }