Observation of the surface 4f state of CePd7 by means of the resonant-inverse-photoemission study at the Ce 4d absorption edge

The resonant inverse photoemission study (RIPES) of CePd7, has been carried out at the Ce 4d-->4f absorption edge. The strong resonant enhancement of the 4f cross section enables us to distinguish two 4f components in the empty electronic state near the Fermi level. The incidence-angle dependence of the RIPES indicates a clear difference between ground-state configurations at the bulk and surface. It is found that the former shows a strongly hybridized 4f state, while the latter shows a localized 4f character. The angle dependence of the RIPES of alpha-Ce metal has been also carried out and similar results as those of CePd7 were obtained. The RIPES at the Ce 4d-->4f edge is found to be a powerful method to investigate the surface 4f state.