title: Communication: The electronic structure of matter probed with a single femtosecond hard x-ray pulse.
abstract: Physical, biological, and chemical transformations are initiated by changes in the electronic configuration of the species involved. These electronic changes occur on the timescales of attoseconds (10(-18) s) to femtoseconds (10(-15) s) and drive all subsequent electronic reorganization as the system moves to a new equilibrium or quasi-equilibrium state. The ability to detect the dynamics of these electronic changes is crucial for understanding the potential energy surfaces upon which chemical and biological reactions take place. Here, we report on the determination of the electronic structure of matter using a single self-seeded femtosecond x-ray pulse from the Linac Coherent Light Source hard x-ray free electron laser. By measuring the high energy resolution off-resonant spectrum (HEROS), we were able to obtain information about the electronic density of states with a single femtosecond x-ray pulse. We show that the unoccupied electronic states of the scattering atom may be determined on a shot-to-shot basis and that the measured spectral shape is independent of the large intensity fluctuations of the incoming x-ray beam. Moreover, we demonstrate the chemical sensitivity and single-shot capability and limitations of HEROS, which enables the technique to track the electronic structural dynamics in matter on femtosecond time scales, making it an ideal probe technique for time-resolved X-ray experiments.
authors.forename: J
authors.initials: J
authors.lastname: Szlachetko
authors.affiliation: Paul Scherrer Institute , Villigen, Switzerland.
authors.forename: C J
authors.initials: CJ
authors.lastname: Milne
authors.affiliation: Department of Physics, University of Fribourg , Fribourg, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Hoszowska
authors.affiliation: Department of Physics, University of Fribourg , Fribourg, Switzerland.
authors.forename: J-Cl
authors.initials: JC
authors.lastname: Dousse
authors.affiliation: Department of Physics, University of Fribourg , Fribourg, Switzerland.
authors.forename: W
authors.initials: W
authors.lastname: Błachucki
authors.affiliation: Paul Scherrer Institute , Villigen, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Sà
authors.affiliation: Paul Scherrer Institute , Villigen, Switzerland.
authors.forename: Y
authors.initials: Y
authors.lastname: Kayser
authors.affiliation: Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory , Menlo Park, California 94025, USA.
authors.forename: M
authors.initials: M
authors.lastname: Messerschmidt
authors.affiliation: Paul Scherrer Institute , Villigen, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Abela
authors.affiliation: Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory , Menlo Park, California 94025, USA.
authors.forename: S
authors.initials: S
authors.lastname: Boutet
authors.affiliation: Paul Scherrer Institute , Villigen, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: David
authors.affiliation: Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory , Menlo Park, California 94025, USA.
authors.forename: G
authors.initials: G
authors.lastname: Williams
authors.affiliation: Institute of Physics, Jan Kochanowski University , Kielce, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Pajek
authors.affiliation: Paul Scherrer Institute , Villigen, Switzerland.
authors.forename: B D
authors.initials: BD
authors.lastname: Patterson
authors.affiliation: Paul Scherrer Institute , Villigen, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Smolentsev
authors.forename: J A
authors.initials: JA
authors.lastname: van Bokhoven
authors.affiliation: Paul Scherrer Institute , Villigen, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Nachtegaal