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

The interactions of O, HO, CO, CO, NO, NO, NO, HS and SO 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 (CO) to complex molecular and dissociative adsorptions leading to surface phases of a few monolayers thickness (O, NO, NO). 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, NO and SO the reactions are very complex.