Photoemission from C0 on Pt(111) using synchrotron radiation in the range 40 eV < = h/2πω < = 150 eV

Photoelectron spectra for C0 adsorbed on the (111)-face of Pt have been measured using synchrotron radiation of energy 40 eV <= h2πω <= 150 eV. A dramatic increase of the molecular orbital (MO) intensity relative to the intensity of the Pt 5d valence band (VB) is observed for h2πω > 100 eV, to a ratio at h2πω = 150 eV that is a factor of three higher than at H2πω = 40 eV. The energy variation of the Pt 5d VB photoemission peak intensity has been derived independently in the 40-200 eV range from measurements on clean Pt. The 5d 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 5d VB is attributed to this cross-section effect. The Pt VB peak nearest the Fermi energy which is mainly tsub(2g) in character, is found to decrease in intensity on adsorption of C0. In the present case synchrotron radiation in the h2πω>100 eV range appears to be especially valuable for studies of adsorbants. (author)