Photoemission from Co on Pt(111) using synchrotron radiation in the range 40 eV ⩽ ħω ⩽ 150 eV

Abstract

Photoelectron spectra for CO adsorbed on the (111)-face of Pt have been measured using synchrotron radiation of energy 40 eV ⩽ ħω ⩽ 150 eV. A dramatic increase of the molecular orbital (MO) intensity relative to the intensity of the Pt 5 d valence band (VB) is observed for ħω > 100 eV, to a ratio at h ̵ ω = 150 eV that is a factor of three higher than at h ̵ ω = 40 eV . The energy variation of the Pt 5 d VB photoemission peak intensity has been derived independently in the 40–200 eV range from measurements on clean Pt. The 5 d peak intensity is found to decrease steeply (by more than an order of magnitude) between 100 and 150 eV. The observed increase of the MO peak intensity relative to that of the 5 d VB is attributed to this cross-section effect. The Pt VB peak nearest the Fermi energy which is mainly t 2g in character, is found to decrease in intensity on adsorption of CO. In the present case synchrotron radiation in the ħω > 100 eV range appears to be especially valuable for studies of adsorbates.