XPS and UPS studies of the adsorption of small molecules on polycrystalline Ni films
Abstract
The interactions of O<inf>2</inf>, H<inf>2</inf>O, CO, CO<inf>2</inf>, NO, N<inf>2</inf>O, NO<inf>2</inf>, H<inf>2</inf>S and SO<inf>2</inf> with evaporated nickel films have been studied over temperatures of 77 to 400 K and adsorbate pressures of 10<sup>-8</sup> Torr to several Torr. The reactions range from reversible adsorption at 77 K only (CO<inf>2</inf>) to complex molecular and dissociative adsorptions leading to surface phases of a few monolayers thickness (O<inf>2</inf>, NO, NO<inf>2</inf>). 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<inf>2</inf> and SO<inf>2</inf> the reactions are very complex.