Temperature Independence of the Angle-Resolved X-Ray Photo-Emission Spectra of Gold and Platinum Valence Bands

Angle-resolved valence-band X-ray photo-emission spectra were taken the \111\ and \100\ directions of Au single crystals and along the \100\ direction of a Pt single crystal at room temperature (293 deg K) and on a probe cooled nearly to liquid N temperature (77 deg K). No change was on cooling the samples, in contrast to expectations based on a simple direct-transition model. A simple 'matrix-element' model appears to predict spectra well even at low temperatures, perhaps because the complexity of the high-energy final-state bands permits sampling effectively throughout the zone. 15 ref.--BA