@article{JayNorellEckertetal.2018,
  author    = {Jay, Raphael M. and Norell, Jesper and Eckert, Sebastian and Hantschmann, Markus and Beye, Martin and Kennedy, Brian and Quevedo, Wilson and Schlotter, William F. and Dakovski, Georgi L. and Minitti, Michael P. and Hoffmann, Matthias C. and Mitra, Ankush and Moeller, Stefan P. and Nordlund, Dennis and Zhang, Wenkai and Liang, Huiyang W. and Kunnus, Kristian and Kubicek, Katharina and Techert, Simone A. and Lundberg, Marcus and Wernet, Philippe and Gaffney, Kelly and Odelius, Michael and F{\"o}hlisch, Alexander},
  title     = {Disentangling Transient Charge Density and Metal-Ligand Covalency in Photoexcited Ferricyanide with Femtosecond Resonant Inelastic Soft X-ray Scattering},
  series = {The journal of physical chemistry letters},
  volume    = {9},
  journal   = {The journal of physical chemistry letters},
  number    = {12},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/acs.jpclett.8b01429},
  pages     = {3538 -- 3543},
  year      = {2018},
  abstract  = {Soft X-ray spectroscopies are ideal probes of the local valence electronic structure of photocatalytically active metal sites. Here, we apply the selectivity of time resolved resonant inelastic X-ray scattering at the iron L-edge to the transient charge distribution of an optically excited charge-transfer state in aqueous ferricyanide. Through comparison to steady-state spectra and quantum chemical calculations, the coupled effects of valence-shell closing and ligand-hole creation are experimentally and theoretically disentangled and described in terms of orbital occupancy, metal-ligand covalency, and ligand field splitting, thereby extending established steady-state concepts to the excited-state domain. pi-Back-donation is found to be mainly determined by the metal site occupation, whereas the ligand hole instead influences sigma-donation. Our results demonstrate how ultrafast resonant inelastic X-ray scattering can help characterize local charge distributions around catalytic metal centers in short-lived charge-transfer excited states, as a step toward future rationalization and tailoring of photocatalytic capabilities of transition-metal complexes.},
  language  = {en}
}
@article{LeitnerJosefssonMazzaetal.2018,
  author    = {Leitner, T. and Josefsson, Ida and Mazza, T. and Miedema, Piter S. and Schr{\"o}der, H. and Beye, Martin and Kunnus, Kristjan and Schreck, S. and D{\"u}sterer, Stefan and F{\"o}hlisch, Alexander and Meyer, M. and Odelius, Michael and Wernet, Philippe},
  title     = {Time-resolved electron spectroscopy for chemical analysis of photodissociation},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {149},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.5035149},
  pages     = {12},
  year      = {2018},
  abstract  = {The prototypical photoinduced dissociation of Fe(CO)(5) in the gas phase is used to test time-resolved x-ray photoelectron spectroscopy for studying photochemical reactions. Upon one-photon excitation at 266 nm, Fe(CO)(5) successively dissociates to Fe(CO)(4) and Fe(CO)(3) along a pathway where both fragments retain the singlet multiplicity of Fe(CO)(5). The x-ray free-electron laser FLASH is used to probe the reaction intermediates Fe(CO)(4) and Fe(CO)(3) with time-resolved valence and core-level photoelectron spectroscopy, and experimental results are interpreted with ab initio quantum chemical calculations. Changes in the valence photoelectron spectra are shown to reflect changes in the valenceorbital interactions upon Fe-CO dissociation, thereby validating fundamental theoretical concepts in Fe-CO bonding. Chemical shifts of CO 3 sigma inner-valence and Fe 3 sigma core-level binding energies are shown to correlate with changes in the coordination number of the Fe center. We interpret this with coordination-dependent charge localization and core-hole screening based on calculated changes in electron densities upon core-hole creation in the final ionic states. This extends the established capabilities of steady-state electron spectroscopy for chemical analysis to time-resolved investigations. It could also serve as a benchmark for howcharge and spin density changes in molecular dissociation and excited-state dynamics are expressed in valence and core-level photoelectron spectroscopy. Published by AIP Publishing.},
  language  = {en}
}
@article{PontiusBeyeTrabantetal.2018,
  author    = {Pontius, Niko and Beye, Martin and Trabant, Christoph and Mitzner, Rolf and Sorgenfrei, Florian 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}
}
@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 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     = {Untersuchung unabh{\"a}ngiger N-H- und N-C-Bindungsverformungen auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung},
  series = {Angewandte Chemie},
  volume    = {129},
  journal   = {Angewandte Chemie},
  number    = {22},
  issn      = {1521-3757},
  doi       = {10.1002/ange.201700239},
  pages     = {6184 -- 6188},
  year      = {2017},
  abstract  = {Die Femtosekundendynamik nach resonanten Photoanregungen mit optischen und R{\"o}ntgenpulsen erm{\"o}glicht eine selektive Verformung von chemischen N-H- und N-C-Bindungen in 2-Thiopyridon in w{\"a}ssriger L{\"o}sung. Die Untersuchung der orbitalspezifischen elektronischen Struktur und ihrer Dynamik auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung an der N1s-Resonanz am Synchrotron und dem Freie-Elektronen-Laser LCLS in Kombination mit quantenchemischen Multikonfigurationsberechnungen erbringen den direkten Nachweis dieser kontrollierten photoinduzierten Molek{\"u}lverformungen und ihrer ultrakurzen Zeitskala.},
  language  = {de}
}
@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     = {Untersuchung unabh{\"a}ngiger N-H- und N-C-Bindungsverformungen auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1121},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-43668},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436688},
  pages     = {7},
  year      = {2017},
  abstract  = {Die Femtosekundendynamik nach resonanten Photoanregungen mit optischen und R{\"o}ntgenpulsen erm{\"o}glicht eine selektive Verformung von chemischen N-H- und N-C-Bindungen in 2-Thiopyridon in w{\"a}ssriger L{\"o}sung. Die Untersuchung der orbitalspezifischen elektronischen Struktur und ihrer Dynamik auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung an der N1s-Resonanz am Synchrotron und dem Freie-Elektronen-Laser LCLS in Kombination mit quantenchemischen Multikonfigurationsberechnungen erbringen den direkten Nachweis dieser kontrollierten photoinduzierten Molek{\"u}lverformungen und ihrer ultrakurzen Zeitskala.},
  language  = {de}
}
@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{MiedemaThielemannKuehnCalafelletal.2019,
  author    = {Miedema, Piter S. and Thielemann-K{\"u}hn, Nele and Calafell, Irati Alonso and Sch{\"u}ßler-Langeheine, Christian and Beye, Martin},
  title     = {Strain analysis from M-edge resonant inelastic X-ray scattering of nickel oxide films},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {21},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  number    = {38},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/c9cp03593a},
  pages     = {21596 -- 21602},
  year      = {2019},
  abstract  = {Electronic structure modifications due to strain are an effective method for tailoring nano-scale functional materials. Demonstrated on nickel oxide (NiO) thin films, Resonant Inelastic X-ray Scattering (RIXS) at the transition-metal M-2,M-3-edge is shown to be a powerful tool for measuring the electronic structure modification due to strain in the near-surface region. Analyses from the M-2,M-3-edge RIXS in comparison with dedicated crystal field multiplet calculations show distortions in 40 nm NiO grown on a magnesium oxide (MgO) substrate (NiO/MgO) similar to those caused by surface relaxation of bulk NiO. The films of 20 and 10 nm NiO/MgO show slightly larger differences from bulk NiO. Quantitatively, the NiO/MgO samples all are distorted from perfect octahedral (O-h) symmetry with a tetragonal parameter Ds of about -0.1 eV, very close to the Ds distortion from octahedral (O-h) symmetry parameter of -0.11 eV obtained for the surface-near region from a bulk NiO crystal. Comparing the spectra of a 20 nm film of NiO grown on a 20 nm magnetite (Fe3O4) film on a MgO substrate (NiO/Fe3O4/MgO) with the calculated multiplet analyses, the distortion parameter Ds appears to be closer to zero, showing that the surface-near region of this templated film is less distorted from O-h symmetry than the surface-near region in bulk NiO. Finally, the potential of M-2,M-3-edge RIXS for other investigations of strain on electronic structure is discussed.},
  language  = {en}
}
@misc{EckertMiedemaQuevedoetal.2016,
  author    = {Eckert, Sebastian and Miedema, Piter and Quevedo, Wilson and O'Cinneide, B. and Fondell, Mattis and Beye, Martin and Pietzsch, Annette and Ross, Matthew R. and Khalil, Munira and F{\"o}hlisch, Alexander},
  title     = {Molecular structures and protonation state of 2-Mercaptopyridine in aqueous solution},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {953},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-43747},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-437473},
  pages     = {103 -- 106},
  year      = {2016},
  abstract  = {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.},
  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{WernetLeitnerJosefssonetal.2017,
  author    = {Wernet, Philippe and Leitner, T. and Josefsson, Ida and Mazza, T. and Miedema, P. S. and Schroder, H. and Beye, Martin and Kunnus, K. and Schreck, S. and Radcliffe, P. and Dusterer, S. and Meyer, M. and Odelius, Michael and Fohlisch, Alexander},
  title     = {Communication: Direct evidence for sequential dissociation of gas-phase Fe(CO)(5) via a singlet pathway upon excitation at 266 nm},
  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       = {10.1063/1.4984774},
  pages     = {5},
  year      = {2017},
  abstract  = {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.},
  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{EckertMiedemaQuevedoetal.2016,
  author    = {Eckert, Sebastian and Miedema, P. S. and Quevedo, W. and Fondell, Mattis and Beye, Martin and Pietzsch, Annette and Ross, M. and Khalil, M. and F{\"o}hlisch, Alexander},
  title     = {Molecular structures and protonation state of 2-Mercaptopyridine in aqueous solution},
  series = {Chemical physics letters},
  volume    = {647},
  journal   = {Chemical physics letters},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0009-2614},
  doi       = {10.1016/j.cplett.2016.01.050},
  pages     = {103 -- 106},
  year      = {2016},
  abstract  = {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.},
  language  = {en}
}
@article{KunnusJosefssonRajkovicetal.2016,
  author    = {Kunnus, Kristjan and Josefsson, I. and Rajkovic, Ivan and Schreck, Simon and Quevedo, Wilson and Beye, Martin and Weniger, C. and Gruebel, S. and Scholz, M. and Nordlund, D. and Zhang, W. and Hartsock, R. W. and Gaffney, K. J. and Schlotter, W. F. and Turner, J. J. and Kennedy, B. and Hennies, F. and de Groot, F. M. F. and Techert, S. and Odelius, Michael and Wernet, Ph. and F{\"o}hlisch, Alexander},
  title     = {Identification of the dominant photochemical pathways and mechanistic insights to the ultrafast ligand exchange of Fe(CO)(5) to Fe(CO)(4)EtOH},
  series = {Structural dynamics},
  volume    = {3},
  journal   = {Structural dynamics},
  publisher = {American Institute of Physics},
  address   = {Washington},
  issn      = {2329-7778},
  doi       = {10.1063/1.4941602},
  pages     = {16},
  year      = {2016},
  abstract  = {We utilized femtosecond time-resolved resonant inelastic X-ray scattering and ab initio theory to study the transient electronic structure and the photoinduced molecular dynamics of a model metal carbonyl photocatalyst Fe(CO)(5) in ethanol solution. We propose mechanistic explanation for the parallel ultrafast intra-molecular spin crossover and ligation of the Fe(CO)(4) which are observed following a charge transfer photoexcitation of Fe(CO)(5) as reported in our previous study [ Wernet et al., Nature 520, 78 (2015)]. We find that branching of the reaction pathway likely happens in the (1)A(1) state of Fe(CO)(4). A sub-picosecond time constant of the spin crossover from B-1(2) to B-3(2) is rationalized by the proposed B-1(2) -> (1)A(1) -> B-3(2) mechanism. Ultrafast ligation of the B-1(2) Fe(CO)(4) state is significantly faster than the spin-forbidden and diffusion limited ligation process occurring from the B-3(2) Fe(CO)(4) ground state that has been observed in the previous studies. We propose that the ultrafast ligation occurs via B-1(2) -> (1)A(1) -> (1)A'Fe(CO)(4)EtOH pathway and the time scale of the (1)A(1) Fe(CO)(4) state ligation is governed by the solute-solvent collision frequency. Our study emphasizes the importance of understanding the interaction of molecular excited states with the surrounding environment to explain the relaxation pathways of photoexcited metal carbonyls in solution. (C) 2016 Author(s).},
  language  = {en}
}
@article{BeyeOebergXinetal.2016,
  author    = {Beye, Martin and {\"O}berg, Henrik and Xin, Hongliang and Dakovski, Georgi L. and F{\"o}hlisch, Alexander and Gladh, Jorgen and Hantschmann, Markus and Hieke, Florian and Kaya, Sarp and K{\"u}hn, Danilo and LaRue, Jerry and Mercurio, Giuseppe and Minitti, Michael P. and Mitra, Ankush and Moeller, Stefan P. and Ng, May Ling and Nilsson, Anders and Nordlund, Dennis and Norskov, Jens and {\"O}str{\"o}m, Henrik and Ogasawara, Hirohito and Persson, Mats and Schlotter, William F. and Sellberg, Jonas A. and Wolf, Martin and Abild-Pedersen, Frank and Pettersson, Lars G. M. and Wurth, Wilfried},
  title     = {Chemical Bond Activation Observed with an X-ray Laser},
  series = {The journal of physical chemistry letters},
  volume    = {7},
  journal   = {The journal of physical chemistry letters},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/acs.jpclett.6b01543},
  pages     = {3647 -- 3651},
  year      = {2016},
  abstract  = {The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse.},
  language  = {en}
}
@article{KunnusJosefssonRajkovicetal.2016,
  author    = {Kunnus, Kristjan and Josefsson, Ida and Rajkovic, Ivan and Schreck, Simon and Quevedo, Wilson and Beye, Martin and Gr{\"u}bel, Sebastian and Scholz, Mirko and Nordlund, Dennis and Zhang, Wenkai and Hartsock, Robert W. and Gaffney, Kelly J. and Schlotter, William F. and Turner, Joshua J. and Kennedy, Brian and Hennies, Franz and Techert, Simone and Wernet, Philippe and Odelius, Michael and F{\"o}hlisch, Alexander},
  title     = {Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics},
  series = {NEW JOURNAL OF PHYSICS},
  volume    = {18},
  journal   = {NEW JOURNAL OF PHYSICS},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/18/10/103011},
  pages     = {9},
  year      = {2016},
  abstract  = {Ultrafast electronic and structural dynamics of matter govern rate and selectivity of chemical reactions, as well as phase transitions and efficient switching in functional materials. Since x-rays determine electronic and structural properties with elemental, chemical, orbital and magnetic selectivity, short pulse x-ray sources have become central enablers of ultrafast science. Despite of these strengths, ultrafast x-rays have been poor at picking up excited state moieties from the unexcited ones. With time-resolved anti-Stokes resonant x-ray Raman scattering (AS-RXRS) performed at the LCLS, and ab initio theory we establish background free excited state selectivity in addition to the elemental, chemical, orbital and magnetic selectivity of x-rays. This unparalleled selectivity extracts low concentration excited state species along the pathway of photo induced ligand exchange of Fe(CO)(5) in ethanol. Conceptually a full theoretical treatment of all accessible insights to excited state dynamics with AS-RXRS with transform-limited x-ray pulses is given-which will be covered experimentally by upcoming transform-limited x-ray sources.},
  language  = {en}
}
@article{SellbergMcQueenLaksmonoetal.2015,
  author    = {Sellberg, Jonas A. and McQueen, Trevor A. and Laksmono, Hartawan and Schreck, Simon and Beye, Martin and DePonte, Daniel P. and Kennedy, Brian and Nordlund, Dennis and Sierra, Raymond G. and Schlesinger, Daniel and Tokushima, Takashi and Zhovtobriukh, Iurii and Eckert, Sebastian and Segtnan, Vegard H. and Ogasawara, Hirohito and Kubicek, Katharina and Techert, Simone and Bergmann, Uwe and Dakovski, Georgi L. and Schlotter, William F. and Harada, Yoshihisa and Bogan, Michael J. and Wernet, Philippe and F{\"o}hlisch, Alexander and Pettersson, Lars G. M. and Nilsson, Anders},
  title     = {X-ray emission spectroscopy of bulk liquid water in "no-man's land"},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {142},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4905603},
  pages     = {9},
  year      = {2015},
  abstract  = {The structure of bulk liquid water was recently probed by x-ray scattering below the temperature limit of homogeneous nucleation (T-H) of similar to 232 K [J. A. Sellberg et al., Nature 510, 381-384 (2014)]. Here, we utilize a similar approach to study the structure of bulk liquid water below T-H using oxygen K-edge x-ray emission spectroscopy (XES). Based on previous XES experiments [T. Tokushima et al., Chem. Phys. Lett. 460, 387-400 (2008)] at higher temperatures, we expected the ratio of the 1b(1)' and 1b(1)" peaks associated with the lone-pair orbital in water to change strongly upon deep supercooling as the coordination of the hydrogen (H-) bonds becomes tetrahedral. In contrast, we observed only minor changes in the lone-pair spectral region, challenging an interpretation in terms of two interconverting species. A number of alternative hypotheses to explain the results are put forward and discussed. Although the spectra can be explained by various contributions from these hypotheses, we here emphasize the interpretation that the line shape of each component changes dramatically when approaching lower temperatures, where, in particular, the peak assigned to the proposed disordered component would become more symmetrical as vibrational interference becomes more important. (C) 2015 AIP Publishing LLC.},
  language  = {en}
}
@article{EckertBeyePietzschetal.2015,
  author    = {Eckert, Sebastian and Beye, Martin and Pietzsch, Annette and Quevedo, Wilson and Hantschmann, Markus and Ochmann, Miguel and Ross, Matthew and Minitti, Michael P. and Turner, Joshua J. and Moeller, Stefan P. and Schlotter, William F. and Dakovski, Georgi L. and Khalil, Munira and Huse, Nils and F{\"o}hlisch, Alexander},
  title     = {Principles of femtosecond X-ray/optical cross-correlation with X-ray induced transient optical reflectivity in solids},
  series = {Applied physics letters},
  volume    = {106},
  journal   = {Applied physics letters},
  number    = {6},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0003-6951},
  doi       = {10.1063/1.4907949},
  pages     = {4},
  year      = {2015},
  abstract  = {The discovery of ultrafast X-ray induced optical reflectivity changes enabled the development of X-ray/optical cross correlation techniques at X-ray free electron lasers worldwide. We have now linked through experiment and theory the fundamental excitation and relaxation steps with the transient optical properties in finite solid samples. Therefore, we gain a thorough interpretation and an optimized detection scheme of X-ray induced changes to the refractive index and the X-ray/optical cross correlation response. (C) 2015 AIP Publishing LLC.},
  language  = {en}
}
@article{OstromObergXinetal.2015,
  author    = {Ostrom, H. and Oberg, H. and Xin, H. and Larue, J. and Beye, Martin and Gladh, J. and Ng, M. L. and Sellberg, J. A. and Kaya, S. and Mercurio, G. and Nordlund, D. and Hantschmann, Markus and Hieke, F. and Kuehn, D. and Schlotter, W. F. and Dakovski, G. L. and Turner, J. J. and Minitti, M. P. and Mitra, A. and Moeller, S. P. and F{\"o}hlisch, Alexander and Wolf, M. and Wurth, W. and Persson, Mats and Norskov, J. K. and Abild-Pedersen, Frank and Ogasawara, Hirohito and Pettersson, Lars G. M. and Nilsson, A.},
  title     = {Probing the transition state region in catalytic CO oxidation on Ru},
  series = {Science},
  volume    = {347},
  journal   = {Science},
  number    = {6225},
  publisher = {American Assoc. for the Advancement of Science},
  address   = {Washington},
  issn      = {0036-8075},
  doi       = {10.1126/science.1261747},
  pages     = {978 -- 982},
  year      = {2015},
  abstract  = {Femtosecond x-ray laser pulses are used to probe the carbon monoxide (CO) oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and oxygen (O) on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the OK-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC-O bond lengths close to the transition state (TS). After 1 ps, 10\% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model.},
  language  = {en}
}
@article{Dell'AngelaAnniyevBeyeetal.2015,
  author    = {Dell'Angela, Martina and Anniyev, Toyli and Beye, Martin and Coffee, Ryan and F{\"o}hlisch, Alexander and Gladh, J{\"o}rgen and Kaya, Sarp and Katayama, Tetsuo and Krupin, Oleg and Nilsson, Anders and Nordlund, Dennis and Schlotter, William F. and Sellberg, Jonas A. and Sorgenfrei, Florian and Turner, Joshua J. and {\"O}str{\"O}m, Henrik and Ogasawara, Hirohito and Wolf, Martin and Wurth, Wilfried},
  title     = {Vacuum space charge effects in sub-picosecond soft X-ray photoemission on a molecular adsorbate layer},
  series = {Structural dynamics},
  volume    = {2},
  journal   = {Structural dynamics},
  number    = {2},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {2329-7778},
  doi       = {10.1063/1.4914892},
  pages     = {10},
  year      = {2015},
  abstract  = {Vacuum space charge induced kinetic energy shifts of O 1s and Ru 3d core levels in femtosecond soft X-ray photoemission spectra (PES) have been studied at a free electron laser (FEL) for an oxygen layer on Ru(0001). We fully reproduced the measurements by simulating the in-vacuum expansion of the photoelectrons and demonstrate the space charge contribution of the high-order harmonics in the FEL beam. Employing the same analysis for 400 nm pump-X-ray probe PES, we can disentangle the delay dependent Ru 3d energy shifts into effects induced by space charge and by lattice heating from the femtosecond pump pulse. (C) 2015 Author(s).},
  language  = {en}
}
@article{WernetKunnusJosefssonetal.2015,
  author    = {Wernet, Philippe and Kunnus, Kristjan and Josefsson, Ida and Rajkovic, Ivan and Quevedo, Wilson and Beye, Martin and Schreck, Simon and Gruebel, S. and Scholz, Mirko and Nordlund, Dennis and Zhang, Wenkai and Hartsock, Robert W. and Schlotter, William F. and Turner, Joshua J. and Kennedy, Brian and Hennies, Franz and de Groot, Frank M. F. and Gaffney, Kelly J. and Techert, Simone and Odelius, Michael and F{\"o}hlisch, Alexander},
  title     = {Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)(5) in solution},
  series = {Nature : the international weekly journal of science},
  volume    = {520},
  journal   = {Nature : the international weekly journal of science},
  number    = {7545},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {0028-0836},
  doi       = {10.1038/nature14296},
  pages     = {78 -- 81},
  year      = {2015},
  abstract  = {Transition-metal complexes have long attracted interest for fundamental chemical reactivity studies and possible use in solar energy conversion(1,2). Electronic excitation, ligand loss from the metal centre, or a combination of both, creates changes in charge and spin density at the metal site(3-11) that need to be controlled to optimize complexes for photocatalytic hydrogen production(8) and selective carbon-hydrogen bond activation(9-11). An understanding at the molecular level of how transition-metal complexes catalyse reactions, and in particular of the role of the short-lived and reactive intermediate states involved, will be critical for such optimization. However, suitable methods for detailed characterization of electronic excited states have been lacking. Here we show, with the use of X-ray laser-based femtosecond-resolution spectroscopy and advanced quantum chemical theory to probe the reaction dynamics of the benchmark transition-metal complex Fe(CO)(5) in solution, that the photo-induced removal of CO generates the 16-electron Fe(CO)(4) species, a homogeneous catalyst(12,13) with an electron deficiency at the Fe centre(14,15), in a hitherto unreported excited singlet state that either converts to the triplet ground state or combines with a CO or solvent molecule to regenerate a penta-coordinated Fe species on a sub-picosecond timescale. This finding, which resolves the debate about the relative importance of different spin channels in the photochemistry of Fe(CO)(5) (refs 4, 16-20), was made possible by the ability of femtosecond X-ray spectroscopy to probe frontier-orbital interactions with atom specificity. We expect the method to be broadly applicable in the chemical sciences, and to complement approaches that probe structural dynamics in ultrafast processes.},
  language  = {en}
}