Observation of direct vibrational excitation in gas-surface collisions of CO with Au(111): a new model system for surface dynamics

• Published in: Physical chemistry chemical physics : PCCP 2013-01, Vol.15 (6), p.1863-1867
• Main Authors: SCHÄFER, Tim, BARTELS, Nils, GOLIBRZUCH, Kai, BARTELS, Christof, KÖCKERT, Hansjochen, AUERBACH, Daniel J, KITSOPOULOS, Theofanis N, WODTKE, Alec M
• Format: Article
• Language: English
• Subjects: Accommodation; Adsorption; Carbon monoxide; Carbon Monoxide - chemistry; Chemistry; Collisions; Dynamical systems; Dynamics; Exact sciences and technology; Excitation; Gases - chemistry; General and physical chemistry; Gold - chemistry; Solid-gas interface; Surface chemistry; Surface physical chemistry; Surface Properties; Thermodynamics; Vibration
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c2cp43351f

We report vibrational excitation of CO from its ground (v = 0) to first excited (v = 1) vibrational state in collision with Au(111) at an incidence energy of translation of E(I) = 0.45 eV. Unlike past work, we can exclude an excitation mechanism involving temporary adsorption on the surface followed by thermalization and desorption. The angular distributions of the scattered CO molecules are narrow, consistent with direct scattering occurring on a sub-ps time scale. The absolute excitation probabilities are about 3% of those expected from thermal accommodation. The surface temperature dependence of excitation, which was measured between 373 and 973 K, is Arrhenius-like with an activation energy equal to the energy required for vibrational excitation. Our measurements are consistent with a vibrational excitation mechanism involving coupling of thermally excited electron-hole pairs of the solid to CO vibration.