title: Indication of non-thermal contribution to visible femtosecond laser-induced CO oxidation on Ru(0001).
abstract: We studied CO oxidation on Ru(0001) induced by 400 nm and 800 nm femtosecond laser pulses where we find a branching ratio between CO oxidation and desorption of 1:9 and 1:31, respectively, showing higher selectivity towards CO oxidation for the shorter wavelength excitation. Activation energies computed with density functional theory show discrepancies with values extracted from the experiments, indicating both a mixture between different adsorbed phases and importance of non-adiabatic effects on the effective barrier for oxidation. We simulated the reactions using kinetic modeling based on the two-temperature model of laser-induced energy transfer in the substrate combined with a friction model for the coupling to adsorbate vibrations. This model gives an overall good agreement with experiment except for the substantial difference in yield ratio between CO oxidation and desorption at 400 nm and 800 nm. However, including also the initial, non-thermal effect of electrons transiently excited into antibonding states of the O-Ru bond yielded good agreement with all experimental results.
authors: Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden.
authors: H
authors: H
authors: Öberg
authors: Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden.
authors: J
authors: J
authors: Gladh
authors: Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden.
authors: K
authors: K
authors: Marks
authors: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors: H
authors: H
authors: Ogasawara
authors: Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden.
authors: A
authors: A
authors: Nilsson
authors: Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden.
authors: L G M
authors: LG
authors: Pettersson
authors: Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden.
authors: H
authors: H
authors: Öström