Enhanced collision induced desorption and dissociation of O2 chemisorbed on Ag(001) at grazing incidence

We have investigated desorption and dissociation of O2 chemisorbed on Ag(001) induced by collision with hyperthermal Xe and Ar atoms provided by a supersonic molecular beam. We find that the cross section for both processes increases rapidly with impact energy and with angle of incidence of the inert gas atom. A model is presented which accounts for the observed energy threshold and for the trend in the cross section.