XPS and UPS studies of the interaction of nitrogen‐containing molecules with nickel: The use of binding energy patterns and relative intensities to diagnose surface species

Interactions of N2, N2O, NO, and NO2 with nickel films have been studied by UPS and XPS. UPS can distinguish between molecular and dissociative adsorption in the initial stages. XPS confirms the UPS assignments and can detect the different species formed after more extensive reaction. It also provides information on the surface stoichiometry. The known general trends in differential relaxation energies must be considered when considering the nature of the bonding occurring. N2 is molecularly adsorbed at 80 K into two states. Initial dissociation followed by multilayer molecular condensation occurs for N2O and NO2 at 80 K. NO adsorbs molecularly at 80 K. At 300 K no reaction occurs with N2; N2O dissociates to leave oxygen atoms at low coverage at the surface, and NO and NO2 undergo complex reaction yielding surface oxide, nitride, and various NO states. The end products after high exposure to NO and NO2 are very similar.