Photoemission Studies of Clean and Oxygen-Covered Pt 6(111) x (100)

Employing the enhanced sensitivity obtained by using synchroton radiation near the Cooper minimum for the 5d valence electrons, the oxygen 2p and 2s levels for oxygen chemisorbed on a Pt 6(111) x (100) crystal, were located. The oxygen 2p level is located at -- 6 eV with a full width at half max. of 3 eV and the 2s at -- 21.6 eV. A factor of four difference in saturation coverage is measured between 300 and 120 deg K, but the position and width of the 2p level is independent of temperature. The 1b1 orbital of weakly adsorbed H2O molecules, which has pure O 2p parentage, was also observed; from the intensity of this orbital, it is suggested why it is difficult to observe the oxygen 2p signal at low photon energies. In addition, a strong preferential attenuaiton in the Pt states near Ef for the adsorbed H2O is noted, in spite of the weak nature of the bond. 24 ref. -- BA