ENERGY AND ANGLE DEPENDENCE OF THE INITIAL STICKING COEFFICIENT OF O-2 ON AG(001)

We investigated the dynamics of the adsorption of O-2 on Ag(001) with the supersonic molecular beam technique combined with EEL spectroscopy , TDS and the reflection detector technique. The initial sticking coef ficient S-0 was measured as a function of the impact energy and of the angle of incidence of the molecules at crystal temperatures of 100 an d 300 K, corresponding to molecular and dissociative adsorption, respe ctively. Both regimes are characterized by the same distribution of en ergy-barriers. This indicates that, in analogy to the case of our prev ious investigation of O-2-Ag(110), the main reaction path involves act ivated adsorption into the molecular well, followed eventually by ther mally induced dissociation for T-s>150 K. Again in analogy to O-2-Ag(1 10), the physisorbed state plays no role in the chemisorption process.