Symmetry-resolved CO desorption and oxidation dynamics on O/Ru(0001) probed at the C K-edge by ultrafast X-ray spectroscopy
- Chapman Univ., Orange, CA (United States)
- Stockholm Univ. (Sweden)
- KTH Royal Inst. of Technology, Stockholm (Sweden)
- Columbia Univ., New York, NY (United States)
- Stanford Univ., CA (United States). SUNCAT Center for Interface Science and Catalysis
- SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
- National Research Council (CNR), Trieste (Italy). Inst. of Materials (CNR-IOM)
- National Research Council (CNR), Lecce (Italy). National Inst. for the Physics of Matter (INFM), National Lab. TASC
- Elettra-Sincrotrone Trieste (Italy)
- Consiglio Nazionale delle Ricerche (CNR), Rome (Italy). Istituto di Struttura della Materia (CNR-ISM)
- Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Leiden Univ. (Netherlands)
- National Research Council (CNR), Rome (Italy)
- Stanford Univ., CA (United States)
In this work, 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 (6x10-8 Torr) and O2 (3x10-8 Torr). Under these conditions, we detect two transient CO species with narrow 2π* 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* 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 (2x10-8 Torr) while maintaining the same O2 pressure. At the lower CO pressure, in the CO 2π* 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 towards '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.
- Research Organization:
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; Knut and Alice Wallenberg Foundation; Swedish Research Council (SRC); Helmholtz Association; SIR Foundation; USDOE
- Contributing Organization:
- SUNCAT
- Grant/Contract Number:
- AC02-76SF00515; AC02-05CH11231; FWP 100435; 2016.0042; 2013-8823; VH-NG-1005; Nr RBSI14G7TL; CUP B82I15000910001
- OSTI ID:
- 1890467
- Alternate ID(s):
- OSTI ID: 1894521
- Journal Information:
- Journal of Chemical Physics, Vol. 157, Issue 16; ISSN 0021-9606
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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