Heterolitic photolysis of O2 on Ag(1Â 0Â 0)

It is shown that at high O2- coverage on Ag(1 0 0) photo dissociation by soft X-rays generates oxygen atoms of covalent and of oxidic nature. The former species is obtained also by thermal dissociation and is the only observed product when irradiating at low O2- coverage. The latter one is produced only photochemically and assigned to an Ag oxide. The fragments produced in the photochemical process end up eventually in identical or in different sites, depending on the presence of other O2- molecules in the immediate neighbourhood.