Molecular ethane adsorption dynamics on oxygen-covered Pt(111)

The dynamics of ethane trapping on Pt(111)-p(2 x 2)-O were investigated by supersonic molecular beam techniques at a surface temperature of 100 K. The initial trapping probability was measured in the range of incident energy from 10 to 45 kJ/mol and incident angles from 0 degrees to 60 degrees. A br oad angular distribution of scattered ethane and total energy scaling (E-T cos(0.2) theta) for ethane trapping indicated a corrugated gas-surface pote ntial. Stochastic trajectory simulations employing a potential developed fr om the trapping of ethane on Pt(111) gives quantitative agreement of the me asured initial trapping probabilities over entire ranges of incident energi es and angles. Calculations of energy transfer for ethane after the first b ounce on Pt(111) and Pt(111)-p(2 x 2)-O clearly indicate that interconversi on of parallel and perpendicular momentum and energy transfer to lattice vi brations account primarily for the differences in trapping probabilities be tween ethane on the two surfaces. At glancing incidence trapping is not sig nificantly reduced on the oxygen-covered Pt(111)because the parallel moment um appears to be transferred partially to phonons.