MOLECULAR PROPANE ADSORPTION DYNAMICS ON PT(111)

Supersonic molecular beam techniques and temperature programmed desorption (TPD) were used to study the adsorption dynamics of propane onto clean and propane-covered Pt(111). The propane sticking probability was measured directly as a function of incident translational energy, E(i), incident angle, theta(i), and propane coverage, theta(cov), at a surface temperature of 95 K. Under these experimental conditions, propane adsorbs molecularly onto Pt(111) terrace sites. Non-normal energy scaling is observed at all propane coverages indicating the importance of parallel momentum in the adsorption process. At all incident translational energies and angles studied, the sticking probability on a propane covered surface, S(theta(cov)), increases with increasing propane coverage. Upon saturation of the Pt(111) terrace sites, spontaneous desorption is observed in the direct adsorption probability experiments.