Inelastic collision processes of methane and ethane molecules at a Pt(111)surface studied by molecular beam scattering techniques

Despite distinct differences in molecular structures and chemical bonds of various alkanes, the inelastic collision processes of CH4 and C2H6, on a Pt (111) surface have been found to be very similar. Both processes can be exp lained qualitatively by a simple classical binary collision model. Angular intensity distributions of reflected molecules of both species indicate tha t direct inelastic collision is primarily governed by the molecular mass, t he incident kinetic energy of the molecule and the surface temperature of t he Pt(111). Other factors such as the molecular structure and chemical bond play minor roles in the process. However, the degree of inelastic collisio n, that is, the energy transfer rate per collision, increases with the mole cular mass. Helium atom scattering has revealed that the dissociation proce ss on the surface is identical for both molecules depending on the incident energy and the surface temperature, as methyl moiety, ethylidyne moiety an d complete decomposition into carbon and hydrogen atoms, successively. At e levated surface temperatures, however, thermally assisted hydrogen tunnelin g appears to dominate ethane dissociation.