Abstract
We investigated the translational incidence energy (Ei) and surface temperature (Ts) dependence of CO vibrational excitation upon scattering from a clean Au(111) surface. We report absolute v = 0 → 1 excitation probabilities for Ei between 0.16 and 0.84 eV and Ts between 473 and 973 K. This is now only the second collision system where such comprehensive measurements are available - the first is NO on Au(111). For CO on Au(111), vibrational excitation occurs via direct inelastic scattering through electron hole pair mediated energy transfer - it is enhanced by incidence translation and the electronically non-adiabatic coupling is about 5 times weaker than in NO scattering from Au(111). Vibrational excitation via the trapping desorption channel dominates at Ei = 0.16 eV and quickly disappears at higher Ei.
Highlights
Kay and co-workers4 have shown that the vibrational excitation probability of NH3 scattered from a Au(111) surface increases monotonically with the translational incidence energy (Ei) above a threshold close to the vibrational excitation energy
The vibrational excitation occurs via coupling of the molecular vibration to the hot electron hole pairs of the metal (EHP-V)
We report comprehensive measurements of absolute vibrational excitation probabilities for the recently reported EHP-V energy transfer for CO collisions with Au(111)
Summary
Studying vibrational energy transfer between small molecules and well defined surfaces provides insights into mechanisms of energy flow relevant to adsorbate surface chemistry. For example, Kay and co-workers have shown that the vibrational excitation probability of NH3 (umbrella mode) scattered from a Au(111) surface increases monotonically with the translational incidence energy (Ei) above a threshold close to the vibrational excitation energy. While the translational incidence energy of NO molecules enhanced vibrational excitation, no threshold was observed. In this case, the vibrational excitation occurs via coupling of the molecular vibration to the hot electron hole pairs of the metal (EHP-V). We report comprehensive measurements of absolute vibrational excitation probabilities for the recently reported EHP-V energy transfer for CO collisions with Au(111).. We report comprehensive measurements of absolute vibrational excitation probabilities for the recently reported EHP-V energy transfer for CO collisions with Au(111).15 This system behaves to NO on Ag/Au, but it is complicated by the presence of trapping/desorption, which is important at low Ei.. We report comprehensive measurements of absolute vibrational excitation probabilities for the recently reported EHP-V energy transfer for CO collisions with Au(111). This system behaves to NO on Ag/Au, but it is complicated by the presence of trapping/desorption, which is important at low Ei. Making use of absolute vibrational excitation probabilities, we characterize the two channels contributing to vibrational excitation of CO on Au(111)
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