%0 Journal Article
%A LaRue, Jerry
%A Liu, Boyang
%A Rodrigues, Gabriel L. S.
%A Liu, Chang
%A Garrido Torres, Jose Antonio
%A Schreck, Simon
%A Diesen, Elias
%A Weston, Matthew
%A Ogasawara, Hirohito
%A Perakis, Fivos
%A Dell’Angela, Martina
%A Capotondi, Flavio
%A Ball, Devon
%A Carnahan, Conner
%A Zeri, Gary
%A Giannessi, Luca
%A Pedersoli, Emanuele
%A Naumenko, Denys
%A Amann, Peter
%A Nikolov, Ivaylo
%A Raimondi, Lorenzo
%A Spezzani, Carlo
%A Beye, Martin
%A Voss, Johannes
%A Wang, Hsin-Yi
%A Cavalca, Filippo
%A Gladh, Jörgen
%A Koroidov, Sergey
%A Abild-Pedersen, Frank
%A Kolb, Manuel
%A Miedema, Piter S.
%A Costantini, Roberto
%A Heinz, Tony F.
%A Luntz, Alan C.
%A Pettersson, Lars G. M.
%A Nilsson, Anders
%T Symmetry-resolved CO desorption and oxidation dynamics on O/Ru(0001) probed at the C K-edge by ultrafast x-ray spectroscopy
%J The journal of chemical physics
%V 157
%N 16
%@ 0021-9606
%C Melville, NY
%I American Institute of Physics
%M PUBDB-2022-05333
%P 164705 
%D 2022
%X We report on carbon monoxide desorption and oxidation induced by 400 nm femtosecond laser excitation on the O/Ru(0001) surface probed by time-resolved x-ray absorption spectroscopy (TR-XAS) at the carbon K-edge. The experiments were performed under constant background pressures of CO (6 × 10<sup>−8</sup> Torr) and O<sub>2</sub> (3 × 10<sup>−8</sup> Torr). Under these conditions, we detect two transient CO species with narrow 2π<sup>*</sup> peaks, suggesting little 2π* interaction with the surface. Based on polarization measurements, we find that these two species have opposing orientations: (1) CO favoring a more perpendicular orientation and (2) CO favoring a more parallel orientation with respect to the surface. We also directly detect gas-phase CO2 using a mass spectrometer and observe weak signatures of bent adsorbed CO2 at slightly higher x-ray energies than the 2π<sup>*</sup> region. These results are compared to previously reported TR-XAS results at the O K-edge, where the CO background pressure was three times lower (2 × 10<sup>−8</sup> Torr) while maintaining the same O<sub>2</sub> pressure. At the lower CO pressure, in the CO 2π<sup>*</sup> region, we observed adsorbed CO and a distribution of OC–O bond lengths close to the CO oxidation transition state, with little indication of gas-like CO. The shift toward “gas-like” CO species may be explained by the higher CO exposure, which blocks O adsorption, decreasing O coverage and increasing CO coverage. These effects decrease the CO desorption barrier through dipole–dipole interaction while simultaneously increasing the CO oxidation barrier. 
%F PUB:(DE-HGF)16
%9 Journal Article
%$ 36319417
%U <Go to ISI:>//WOS:000876502600007
%R 10.1063/5.0114399
%U https://bib-pubdb1.desy.de/record/483446