Electronic-Energy-Level Measurements of Chemisorbed Oxygen on the (100) Plane of Nickel by Electron Energy-Loss Spectroscopy

Energy-loss spectra of low-energy electrons reflected from the nickel (100) plane were measured as a function of coverage by oxygen. A characteristic energy loss at 5.8 eV was observed in the $p(2\mathrm{}\times 2)$ arrangement. This loss peak splits into 5.4 and 6.4 eV in $c(2\mathrm{}\times 2)$. These peaks are caused by excitation of electrons in chemisorption bonds of nickel-oxygen. The split shows the change in bond nature in the different coverages of oxygen on Ni(100).