A study of core and valence levels in beta-PbO2 by hard X-ray photoemission

The core and valence levels of beta-PbO2 have been studied using hard X-ray photoemission spectroscopy (hv = 6000 eV and 7700 eV). The Pb 4f core levels display an asymmetric lineshape which may be fitted with components associated with screened and unscreened final states. It is found that intrinsic final state screening is suppressed in the near-surface region. A shift in the O 1s binding energy due to recoil effects is observed under excitation at 7700 eV. It is shown that conduction band states have substantial 6s character and are selectively enhanced in hard X-ray photoemission spectra. However, the maximum amplitude in the Pb 6s partial density of states is found at the bottom of the valence band and the associated photoemission peak shows the most pronounced enhancement in intensity at high photon energy. (C) 2008 Elsevier B.V. All rights reserved.