@article{EhlertKlamroth2020,
  author    = {Ehlert, Christopher and Klamroth, Tillmann},
  title     = {PSIXAS: A Psi4 plugin for efficient simulations of X-ray absorption spectra based on the transition-potential and Delta-Kohn-Sham method},
  series = {Journal of computational chemistry : organic, inorganic, physical, biological},
  volume    = {41},
  journal   = {Journal of computational chemistry : organic, inorganic, physical, biological},
  number    = {19},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0192-8651},
  doi       = {10.1002/jcc.26219},
  pages     = {1781 -- 1789},
  year      = {2020},
  abstract  = {Near edge X-ray absorption fine structure (NEXAFS) spectra and their pump-probe extension (PP-NEXAFS) offer insights into valence- and core-excited states. We present PSIXAS, a recent implementation for simulating NEXAFS and PP-NEXAFS spectra by means of the transition-potential and the Delta-Kohn-Sham method. The approach is implemented in form of a software plugin for the Psi4 code, which provides access to a wide selection of basis sets as well as density functionals. We briefly outline the theoretical foundation and the key aspects of the plugin. Then, we use the plugin to simulate PP-NEXAFS spectra of thymine, a system already investigated by others and us. It is found that larger, extended basis sets are needed to obtain more accurate absolute resonance positions. We further demonstrate that, in contrast to ordinary NEXAFS simulations, where the choice of the density functional plays a minor role for the shape of the spectrum, for PP-NEXAFS simulations the choice of the density functional is important. Especially hybrid functionals (which could not be used straightforwardly before to simulate PP-NEXAFS spectra) and their amount of "Hartree-Fock like" exact exchange affects relative resonance positions in the spectrum.},
  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{RosaPohlenzdeGrouchyetal.2016,
  author    = {Rosa, A. D. and Pohlenz, Julia and de Grouchy, C. and Cochain, B. and Kono, Y. and Pasternak, S. and Mathon, O. and Irifune, T. and Wilke, Max},
  title     = {In situ characterization of liquid network structures at high pressure and temperature using X-ray absorption spectroscopy coupled with the Paris-Edinburgh press},
  series = {High pressure research},
  volume    = {36},
  journal   = {High pressure research},
  publisher = {American Geophysical Union},
  address   = {Abingdon},
  issn      = {0895-7959},
  doi       = {10.1080/08957959.2016.1199693},
  pages     = {332 -- 347},
  year      = {2016},
  abstract  = {We review recent progress in studying structural properties of liquids using X-ray absorption spectroscopy coupled with the Paris-Edinburgh press at third-generation synchrotron facilities. This experimental method allows for detecting subtle changes in atomic arrangements of melts over a wide pressure-temperature range. It has been also employed to monitor variations of the local coordination environment of diluted species contained in glasses, liquids and crystalline phases as a function of the pressure and temperature. Such information is of great importance for gaining deeper insights into the physico-chemical properties of liquids at extreme condition, including the understanding of such phenomena as liquid-liquid phase transitions, viscosity drops and various transport properties of geological melts. Here, we describe the experimental approach and discuss its potential in structural characterization on selected scientific highlights. Finally, the current ongoing instrumental developments and future scientific opportunities are discussed.},
  language  = {en}
}
@article{SternemannWilke2016,
  author    = {Sternemann, C. and Wilke, Max},
  title     = {Spectroscopy of low and intermediate Z elements at extreme conditions: in situ studies of Earth materials at pressure and temperature via X-ray Raman scattering},
  series = {High pressure research},
  volume    = {36},
  journal   = {High pressure research},
  publisher = {IOP Publ. Ltd.},
  address   = {Abingdon},
  issn      = {0895-7959},
  doi       = {10.1080/08957959.2016.1198903},
  pages     = {275 -- 292},
  year      = {2016},
  abstract  = {X-ray Raman scattering spectroscopy is an emerging method in the study of low and intermediate Z elements' core-electron excitations at extreme conditions in order to reveal information on local structure and electronic state of matter in situ. We discuss the capabilities of this method to address questions in Earth materials' science and demonstrate its sensitivity to detect changes in the oxidation state, electronic structure, coordination, and spin state. Examples are presented for the study of the oxygen K-, silicon L- and iron M-edges. We assess the application of both temperature and pressure in such investigations exploiting diamond anvil cells in combination with resistive or laser heating which is required to achieve realistic conditions of the Earth's crust, mantle, and core.},
  language  = {en}
}