Electron hole pair mediated vibrational excitation in CO scattering from Au(111): Incidence energy and surface temperature dependence

We investigated the translational incidence energy (E_i) and surface temperature (T_s) dependence of CO vibrational excitation upon scattering from a clean Au(111) surface. We report absolute v = 0 → 1 excitation probabilities for E_i between 0.16 and 0.84 eV and T_s 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 E_i = 0.16 eV and quickly disappears at higher E_i.