title: Selective ultrafast probing of transient hot chemisorbed and precursor states of CO on Ru(0001).
abstract: We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in the occupied and unoccupied electronic structure using ultrafast soft x-ray absorption and emission. We recently reported [M. Dell'Angela et al. Science 339, 1302 (2013)] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2 ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical laser fluence. Ab initio molecular dynamics simulations of CO adsorbed on Ru(0001) were performed at 1500 and 3000 K providing insight into the desorption process.
authors.affiliation: SIMES, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: M
authors.initials: M
authors.lastname: Beye
authors.forename: T
authors.initials: T
authors.lastname: Anniyev
authors.forename: R
authors.initials: R
authors.lastname: Coffee
authors.forename: M
authors.initials: M
authors.lastname: Dell'Angela
authors.forename: A
authors.initials: A
authors.lastname: Föhlisch
authors.forename: J
authors.initials: J
authors.lastname: Gladh
authors.forename: T
authors.initials: T
authors.lastname: Katayama
authors.forename: S
authors.initials: S
authors.lastname: Kaya
authors.forename: O
authors.initials: O
authors.lastname: Krupin
authors.forename: A
authors.initials: A
authors.lastname: Møgelhøj
authors.forename: A
authors.initials: A
authors.lastname: Nilsson
authors.forename: D
authors.initials: D
authors.lastname: Nordlund
authors.forename: J K
authors.initials: JK
authors.lastname: Nørskov
authors.forename: H
authors.initials: H
authors.lastname: Öberg
authors.forename: H
authors.initials: H
authors.lastname: Ogasawara
authors.forename: L G M
authors.initials: LG
authors.lastname: Pettersson
authors.forename: W F
authors.initials: WF
authors.lastname: Schlotter
authors.forename: J A
authors.initials: JA
authors.lastname: Sellberg
authors.forename: F
authors.initials: F
authors.lastname: Sorgenfrei
authors.forename: J J
authors.initials: JJ
authors.lastname: Turner
authors.forename: M
authors.initials: M
authors.lastname: Wolf
authors.forename: W
authors.initials: W
authors.lastname: Wurth
authors.forename: H
authors.initials: H
authors.lastname: Oström
mesh_terms: D000327:Adsorption; D002248:Carbon Monoxide / Q000737:chemistry*; D007834:Lasers; D056004:Molecular Dynamics Simulation; D060739:Phonons; D012428:Ruthenium / Q000737:chemistry*; D013499:Surface Properties; D056928:X-Ray Absorption Spectroscopy / Q000379:methods
chemical_list: D002248:Carbon Monoxide; D012428:Ruthenium