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 coefficient 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 and 300 K, corresponding to molecular and dissociative adsorption, respectively. Both regimes are characterized by the same distribution of energy-barriers. This indicates that, in analogy to the case of our previous investigation of O-2-Ag(110), the main reaction path involves activated adsorption into the molecular well, followed eventually by thermally induced dissociation for T-s>150 K. Again in analogy to O-2-Ag(110), the physisorbed state plays no role in the chemisorption process.