ON THE ABILITY OF CS-PRECOVERED AND NA-PRECOVERED NI(111) SURFACES TO FORM DIOXYGEN SPECIES UPON OXYGEN EXPOSURE

The adsorption of oxygen on a sodium-precovered (with one full monolayer) Ni(111) surface at 100 K has been examined by means of UP and XP spectroscopies. The O2- ion appears first. Above 5 × 10-5 Pa s, a dioxygen species is formed and at exposures higher than 3 × 10-4 Pa s, Ni-O bonding is observed. Concerning oxygen species, the Na-O-Ni(111) surface which involves a noticeable contribution from the O2- ion, differs from the Cs-O-Ni(111) surface where dioxygen species dominate. © 1990 Pergamon Press plc.