XPS and UPS studies of the adsorption of small molecules on polycrystalline Ni films

Abstract

The interactions of O₂, H₂O, CO, CO₂, NO, N₂O, NO₂, H₂S and SO₂ with evaporated nickel films have been studied over temperatures of 77 to 400 K and adsorbate pressures of 10^–8 Torr to several Torr. The reactions range from reversible adsorption at 77 K only (CO₂) to complex molecular and dissociative adsorptions leading to surface phases of a few monolayers thickness (O₂, NO, NO₂). With the aid of gas-phase data and the spectra of some of the molecules adsorbed on gold at 77 K it is possible to separate non-dissociative and dissociative adsorptions. Proposals concerning the products of dissociation can be made, though for NO, NO₂ and SO₂ the reactions are very complex.