Core-Level XPS Studies of Ce and La Intermetallic Compounds and Their Implications for the 4F Levels of Ce Compounds

摘要

The 3d core hole X-ray photoelectron spectra (XPS) of approximately 30 intermetallic compounds of La and Ce are reported. Transitions to final states with approximately f sup 0 , f sup 1 and f sup 2 character are observed in some Ce compounds (f sup 0 and f sup 1 for La compounds). The results are discussed in terms of the current ideas of the influence of f-counts and f-levels hybridization on core level lineshapes. We cannot find an explanation of the observed spectra consistant with the ''promotial model'' where the 4f-count varies and 4f electron was thought to be entirely promoted to the Ce 5d6s valence bands in some compounds. There may be some small charge transfer from the f level, however. In conjunction with ideas on screening processes in XPS the observed lineshapes suggest coupling of the 4f electrons to other states and is strongest in those compounds previously thought to have f sup 0 character. This coupling increases despite a large increase in the Ce-Ce distance when Ce is diluted with Ni or Pd. Thus it cannot be due to direct f-f interaction and must be attributed to coupling with the other valence electrons; possibly those centered on the partner sites. 89 references. (ERA citation 10:000909)