Electronic structure of a Pt(111)-Ge surface alloy and adsorbed CO

Angle-integrated photoemission spectra are observed for Pt(111) and a Pt(lll)-Ge surface alloy. The spectra for Pt(lll)Ge show d band filling compared with those for Pt(111). Although the chemisorption energy of CO is noticeably reduced by alloy formation, the binding energies of the occupied levels for adsorbed CO are almost the same as those on pure Pt(lll). The results are discussed by the d band filling due to s-d hybridization of Ge s electrons and the Pt d band and by two-level hybridization of the 5 sigma and 2 pi states with the modified d band. (C) 1998 Elsevier Science B.V.