Ultra-violet photoelectron spectroscopy studies of gas adsorption on transition metals

Abstract

The adsorption of CO and C₂H₄ on oriented single crystals of nickel has been studied by means of ultra-violet photoelectron spectroscopy (UPS). At Hel energies (21.2 eV), distinctly different d band densities of states are observed for the clean (111), (110), and (100) faces which are interpreted in terms of bulk rather than surface band calculations. Following CO adsorptions, states derived from the π2p antibonding level of CO may be distinguished in the structure close to E_f in addition to the deeper σ2p and π2p bonding states. The cracking of ethylene at high temperature over Ni(110) is shown to produce graphitic overlayers. Preliminary studies of the oxidation of chromium are also reported.