title: Real-time observation of surface bond breaking with an x-ray laser.
abstract: We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals.
authors.affiliation: University of Hamburg and Center for Free Electron Laser Science, Hamburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Dell'Angela
authors.forename: T
authors.initials: T
authors.lastname: Anniyev
authors.forename: M
authors.initials: M
authors.lastname: Beye
authors.forename: R
authors.initials: R
authors.lastname: Coffee
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: J
authors.initials: J
authors.lastname: LaRue
authors.forename: A
authors.initials: A
authors.lastname: Møgelhøj
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: Oberg
authors.forename: H
authors.initials: H
authors.lastname: Ogasawara
authors.forename: H
authors.initials: H
authors.lastname: Oström
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: A
authors.initials: A
authors.lastname: Nilsson