The Interaction of Hyperthermal Argon Atoms with CO-covered Ru(0001): Scattering and Collision-Induced Desorption

Hyperthermal Ar is scattered at θi=60° from CO-saturated Ru(0001). Collision-induced desorption leads to ejection of fast CO (~1eV). Maximum desorption occurs along the surface normal, but the angular distribution varies with the fractional CO coverage, indicating that the process involves lateral interaction with adjacent molecules. There is no indication of direct recoil events. Incident Ar cannot readily penetrate the saturated overlayer. Scattered Ar has both a fast and a slow component. The slow component is dominant when scattering from the saturated layer. The fast component is due to scattering from CO when the overlayer is intact and from Ru when the layer is partially depleted.