ELECTRONIC-STRUCTURE OF ATOMIC OXYGEN ADSORBED ON NI(100) AND CU(100)STUDIED BY SOFT-X-RAY EMISSION AND PHOTOELECTRON SPECTROSCOPIES

The electronic structure of c(2X2)-O/Ni(100) and p(2 square-root 2 X s quare-root 2)R45-degrees-O/Cu(100) has been studied by soft-x-ray emis sion spectroscopy (SXES), ultraviolet, and x-ray photoemission spectro scopies (UPS and XPS). For O/Ni(100), the 2p-derived states are center ed at 6 eV below the Fermi level. There is intensity from these states all the way up to the Fermi level, due to the 2p-3d hybridization. Th e sharp edge of the SXES intensity at the Fermi edge indicates that th e antibonding 2p-3d states are partly occupied. This is also manifeste d in the asymmetric line shape of the O 1s XPS peak. In O/Cu(100), on the other hand, these states are close to fully occupied, and observed around 1-2 eV binding energy in the UP and SXE spectra. The higher en ergies of the excitations from the filled 2p-3d states result in a dis crete satellite about 3 eV from the O 1s main line in the O/Cu(100) XP S spectrum. The main SXES intensity is positioned at about 4-5 eV, i.e ., in the region of the Cu d band, indicating a larger O-Cu hybridizat ion in this energy region that previously reported.