Sub-surface incorporation of oxygen on Ag(001) during molecular dissociation

We report evidence for the occurrence of sub-surface oxygen incorporation during the dissociation process of admolecules. The process is observed for O2 chemisorbed on Ag(001) at a surface temperature of 100 K, where thermally activated sub-surface diffusion is inactive. The phenomenon occurs both when dissociation is induced thermally or by electron bombardment. EELS peaks corresponding to the vibration of adatoms and of sub-surface oxygen are observed.