title: Observing Solvation Dynamics with Simultaneous Femtosecond X-ray Emission Spectroscopy and X-ray Scattering.
abstract: In liquid phase chemistry dynamic solute-solvent interactions often govern the path, ultimate outcome, and efficiency of chemical reactions. These steps involve many-body movements on subpicosecond time scales and thus ultrafast structural tools capable of capturing both intramolecular electronic and structural changes, and local solvent structural changes are desired. We have studied the intra- and intermolecular dynamics of a model chromophore, aqueous [Fe(bpy)3](2+), with complementary X-ray tools in a single experiment exploiting intense XFEL radiation as a probe. We monitored the ultrafast structural rearrangement of the solute with X-ray emission spectroscopy, thus establishing time zero for the ensuing X-ray diffuse scattering analysis. The simultaneously recorded X-ray diffuse scattering patterns reveal slower subpicosecond dynamics triggered by the intramolecular structural dynamics of the photoexcited solute. By simultaneous combination of both methods only, we can extract new information about the solvation dynamic processes unfolding during the first picosecond (ps). The measured bulk solvent density increase of 0.2% indicates a dramatic change of the solvation shell around each photoexcited solute, confirming previous ab initio molecular dynamics simulations. Structural changes in the aqueous solvent associated with density and temperature changes occur with ∼1 ps time constants, characteristic for structural dynamics in water. This slower time scale of the solvent response allows us to directly observe the structure of the excited solute molecules well before the solvent contributions become dominant.
authors.affiliation: Department of Physics, Technical University of Denmark , Fysikvej 307, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Haldrup
authors.affiliation: European XFEL GmbH , Albert-Einstein-Ring 19, D-22761 Hamburg, Germany.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Gawelda
authors.affiliation: Paul Scherrer Institut, SwissFEL, CH-5232 Villigen PSI, Switzerland.
authors.forename: Rafael
authors.initials: R
authors.lastname: Abela
authors.affiliation: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
authors.forename: Roberto
authors.initials: R
authors.lastname: Alonso-Mori
authors.affiliation: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
authors.forename: Uwe
authors.initials: U
authors.lastname: Bergmann
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary.
authors.forename: Amélie
authors.initials: A
authors.lastname: Bordage
authors.affiliation: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
authors.forename: Marco
authors.initials: M
authors.lastname: Cammarata
authors.affiliation: Department of Chemical Physics, Lund University , Box 118, S-22100 Lund, Sweden.
authors.forename: Sophie E
authors.initials: SE
authors.lastname: Canton
authors.affiliation: Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Asmus O
authors.initials: AO
authors.lastname: Dohn
authors.affiliation: Department of Physics, Technical University of Denmark , Fysikvej 307, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Tim Brandt
authors.initials: TB
authors.lastname: van Driel
authors.affiliation: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
authors.forename: David M
authors.initials: DM
authors.lastname: Fritz
authors.affiliation: European XFEL GmbH , Albert-Einstein-Ring 19, D-22761 Hamburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Galler
authors.affiliation: European Synchrotron Radiation Facility , F-38043 Grenoble Cedex 9, France.
authors.forename: Pieter
authors.initials: P
authors.lastname: Glatzel
authors.affiliation: Department of Chemical Physics, Lund University , Box 118, S-22100 Lund, Sweden.
authors.forename: Tobias
authors.initials: T
authors.lastname: Harlang
authors.affiliation: Department of Physics, Technical University of Denmark , Fysikvej 307, DK-2800 Kongens Lyngby, Denmark.|Department of Chemical Physics, Lund University , Box 118, S-22100 Lund, Sweden.
authors.forename: Kasper S
authors.initials: KS
authors.lastname: Kjær
authors.affiliation: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.|Paul Scherrer Institut, SwissFEL, CH-5232 Villigen PSI, Switzerland.
authors.forename: Henrik T
authors.initials: HT
authors.lastname: Lemke
authors.affiliation: Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Klaus B
authors.initials: KB
authors.lastname: Møller
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Németh
authors.affiliation: Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark.|Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary.
authors.forename: Mátyás
authors.initials: M
authors.lastname: Pápai
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary.
authors.forename: Norbert
authors.initials: N
authors.lastname: Sas
authors.affiliation: Department of Chemical Physics, Lund University , Box 118, S-22100 Lund, Sweden.
authors.forename: Jens
authors.initials: J
authors.lastname: Uhlig
authors.affiliation: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
authors.forename: Diling
authors.initials: D
authors.lastname: Zhu
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary.
authors.forename: György
authors.initials: G
authors.lastname: Vankó
authors.affiliation: Department of Chemical Physics, Lund University , Box 118, S-22100 Lund, Sweden.
authors.forename: Villy
authors.initials: V
authors.lastname: Sundström
authors.affiliation: Department of Physics, Technical University of Denmark , Fysikvej 307, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Martin M
authors.initials: MM
authors.lastname: Nielsen
authors.affiliation: European XFEL GmbH , Albert-Einstein-Ring 19, D-22761 Hamburg, Germany.|The Hamburg Center for Ultrafast Imaging, Universität Hamburg , Luruper Chaussee 149, D-22761 Hamburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Bressler