title: Density functional simulation of resonant inelastic X-ray scattering experiments in liquids: acetonitrile.
abstract: In this paper we report an experimental and computational study of liquid acetonitrile (H3C-C[triple bond, length as m-dash]N) by resonant inelastic X-ray scattering (RIXS) at the N K-edge. The experimental spectra exhibit clear signatures of the electronic structure of the valence states at the N site and incident-beam-polarization dependence is observed as well. Moreover, we find fine structure in the quasielastic line that is assigned to finite scattering duration and nuclear relaxation. We present a simple and light-to-evaluate model for the RIXS maps and analyze the experimental data using this model combined with ab initio molecular dynamics simulations. In addition to polarization-dependence and scattering-duration effects, we pinpoint the effects of different types of chemical bonding to the RIXS spectrum and conclude that the H2C-C[double bond, length as m-dash]NH isomer, suggested in the literature, does not exist in detectable quantities. We study solution effects on the scattering spectra with simulations in liquid and in vacuum. The presented model for RIXS proved to be light enough to allow phase-space-sampling and still accurate enough for identification of transition lines in physical chemistry research by RIXS.
authors.affiliation: Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin for Materials and Energy, Albert-Einstein-Str 15, D-12489, Berlin, Germany. johannes.niskanen@helmholtz-berlin.de and Department of Physics, University of Helsinki, Gustav Hällströmin katu 2a, FI-00014, Helsinki, Finland.
authors.forename: Johannes
authors.initials: J
authors.lastname: Niskanen
authors.affiliation: Department of Physics and Astronomy, University of Turku, Vesilinnantie 5, FI-20014 Turku, Finland and Institute of Physics, University of Tartu, W. Ostwaldi 1, EE-50411 Tartu, Estonia.
authors.forename: Kuno
authors.initials: K
authors.lastname: Kooser
authors.affiliation: Department of Physics, University of Helsinki, Gustav Hällströmin katu 2a, FI-00014, Helsinki, Finland.
authors.forename: Jaakko
authors.initials: J
authors.lastname: Koskelo
authors.affiliation: Institute of Physics, University of Tartu, W. Ostwaldi 1, EE-50411 Tartu, Estonia.
authors.forename: Tanel
authors.initials: T
authors.lastname: Käämbre
authors.affiliation: Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin for Materials and Energy, Albert-Einstein-Str 15, D-12489, Berlin, Germany. johannes.niskanen@helmholtz-berlin.de and Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, D-14476 Potsdam, Germany.
authors.forename: Kristjan
authors.initials: K
authors.lastname: Kunnus
authors.affiliation: Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin for Materials and Energy, Albert-Einstein-Str 15, D-12489, Berlin, Germany. johannes.niskanen@helmholtz-berlin.de.
authors.forename: Annette
authors.initials: A
authors.lastname: Pietzsch
authors.affiliation: Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin for Materials and Energy, Albert-Einstein-Str 15, D-12489, Berlin, Germany. johannes.niskanen@helmholtz-berlin.de.
authors.forename: Wilson
authors.initials: W
authors.lastname: Quevedo
authors.affiliation: Department of Physics, University of Helsinki, Gustav Hällströmin katu 2a, FI-00014, Helsinki, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Hakala
authors.affiliation: Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin for Materials and Energy, Albert-Einstein-Str 15, D-12489, Berlin, Germany. johannes.niskanen@helmholtz-berlin.de and Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, D-14476 Potsdam, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Föhlisch
authors.affiliation: Department of Physics, University of Helsinki, Gustav Hällströmin katu 2a, FI-00014, Helsinki, Finland.
authors.forename: Simo
authors.initials: S
authors.lastname: Huotari
authors.affiliation: Department of Physics and Astronomy, University of Turku, Vesilinnantie 5, FI-20014 Turku, Finland.
authors.forename: Edwin
authors.initials: E
authors.lastname: Kukk