Electronic structure of Ce and its intermetallic compounds

We report the core-level x-ray photoelectron spectroscopy spectra of 30 intermetallic compounds of La and Ce. The results are discussed in the light of calculations using the Anderson impurity model of the $4f$ levels and including the degeneracy of the $4f$ levels. The comparison allows us to derive values for the coupling between the $f$ levels and the conduction states $\Delta$ and the number of $4f$ electrons $n_f$. We find $\Delta$ to be up to ∼ 150 meV in some Ce intermetallic compounds, and find $n_f$ to range from ∼0.8-1.1. We cannot reconcile the core-level results with the traditional promotional model in which $\Delta$ was assumed to be 10 meV or less and the $f$-electron count could range from 1 down to zero in Ce intermetallic compounds.