The molecular adsorption of ethane on sulfur- and ethylidyne-covered surfaces of Pt(111)

Abstract Initial adsorption probabilities, α 0 , were determined for ethane incident on sulfur- and ethylidyne-covered surfaces of Pt(111) at 95 K for incident translational energies from 10 to 44 kJ mol −1 and incident angles from 0 to 60°. At normal incidence and for all translational energies studied, α 0 on these surfaces was found to be enhanced relative to clean Pt(111). The initial adsorption probabilities on both adsorbate-covered surfaces were found to be independent of the angle of incidence, suggesting a highly corrugated static gas-surface potential. The interconversion of normal and parallel momenta due to this corrugation appears to be the mechanism which best explains these results. The notion of increased energy transfer from a match in mass of the collision partners (ethane/sulfur) is clearly not consistent with the data, since the adsorption probability of ethane on the sulfur-covered surface at glancing incidence (60°) is less than that on the clean surface at this same angle. Ethylidyne was found to increase α 0 more than sulfur for all incident conditions, apparently due to energy transfer to the internal degrees of freedom of ethylidyne, a mechanism which is not available to the sulfur adsorbate.