The electronic structure of PdO found by photoemission (UPS and XPS) and inverse photoemission (BIS)

The electronic structure of the 4d transition-metal oxide PdO is investigated by photoemission (UPS and XPS), inverse photoemission (BIS; ), and electron energy loss spectroscopy in reflection geometry (REELS; primary energy, ). The valence band spectra are compared to recent theoretical ab initio band-structure calculations. Good agreement between theory and experiment is found in the occupied part of the band structure down to 8 eV below as well as in the unoccupied part up to 6 eV above . This confirms the common view that the electronic structure of the 4d transition-metal oxides, e.g. PdO, can be explained in terms of a single-electron picture. Nevertheless correlation effects among the Pd 4d electrons are clearly visible in the spectra, as e.g. satellites of the Pd core level spectra. In order to explain the origin of these satellites we performed simple cluster model calculations and as a result we can explain one satellite in a screening picture by means of a charge transfer process. In addition radiation damage effects in PdO during the electron bombardment in the BIS experiments are reported. This is explained by the formation of the Pd -like states connected with oxygen loss due to the electron bombardment.