O-2 CHEMISORPTION ON COO(100) - A RESONANT-PHOTOEMISSION STUDY

The changes in the electronic structure of reduced single-crystal CoO(100) surfaces upon exposure to O2 have been studied by means of resonant photoemission with use of synchrotron radiation. O-vacancy point defects on CoO(100) interact strongly with O2 at room temperature. Ultraviolet photoemission difference spectra of the valence-band region taken before and after 10(3) L of O2 exposure (1 L = 10(-6) Torrsec) exhibit predominantly a 3d6-like final-state resonant behavior, which results from changes in substrate electronic structure arising from the reestablishment of Co-O ionic bonding on the surface upon O2 exposure. Although most of the O2 is believed to chemisorb as O2-, other adsorbed oxygen species are also present.