4f-Derived Resonant Photoemission in the Early Rare Earths: Possible Evidence for Localized Screening Channel

Photoemission studies of $\mathrm{RE}{\mathrm{Ru}}_2$ and $\mathrm{RE}{\mathrm{Pd}}_2$ ($RE=\mathrm{C}\mathrm{e},\mathrm{P}\mathrm{r},\mathrm{N}\mathrm{d}$) reveal two $4f$-derived features with an energy separation of ∼2.5 eV, which move in parallel to larger binding energies in going from Ce to Pr to Nd. These results, which are at variance with predictions of Anderson-model treatments based on the large-orbital-degeneracy approximation, are compatible with the treatments of Liu and Ho and of Riseborough, who distinguished between the two peaks on the basis of their screening geometries.