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

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.

Ion and velocity map imaging for surface dynamics and kinetics

“…1 Deviations from Maxwellian velocity distributions and from cos(θ) (with respect to the surface normal) angular distributions for argon atoms a) daniel.harding@mpibpc.mpg.de desorbing from Pt(111) provided velocity and incidence angle dependent sticking probabilities, again via detailed balance. 8 The surface temperature dependence of the vibrational excitation probabilities of NO, 9 N 2 , 3 and CO 10 on Au(111), combined with the absence of a threshold in the incidence energy dependence provided a fingerprint for the electronically nonadiabatic vibrational excitation. From these examples, it is clear that the experimental observation of the dynamical fingerprints of the different processes controlling surface scattering require accurate measurement of the laboratory-frame speed and angular distributions of scattered molecules as a function of the surface temperature (T s ) and the molecules' incidence energy and initial quantum state.…”

Electron-Mediated Phonon-Phonon Coupling Drives the Vibrational Relaxation of CO on Cu(100)

“…However, in the case of metal surfaces, high concentrations of conducting electrons can, in principle, exchange energy with the adsorbate nuclear degrees of freedom. In fact, there is growing experimental evidence that points out the existence of such nonadiabatic effects [1][2][3][4][5][6][7][8]. Among them, the significant vibrational linewidths of molecules adsorbed on metal surfaces, which are reported in infrared absorption or pump-probe spectroscopy experiments, are considered to be clear fingerprints of the electron-mediated vibrational relaxation [2][3][4][5][6].…”

A simple resonance enhanced laser ionization scheme for CO via the A1Π state

“…Currently, the most powerful analysis technique in molecular dynamics research is the combination of resonance enhanced multiphoton ionization (REMPI) 1,2 and Velocity Map Imaging (VMI), 3,4 which is used for the study of molecular dynamics processes including rotational energy transfer, 5 photodissociation, 6 and surface scattering. 7,8 REMPI-VMI combines the sensitivity and quantum state selection of REMPI with the high information content on nascent product velocity provided by VMI. For any molecular dynamics study using REMPI, a well-characterized ionization scheme is necessary.…”