Inelastic electron scattering spectra of normal and mixed-valent samarium compounds

Electron-energy-loss spectra of the Sm $3d$ (or $4d$) core level are found to be identical to within ≈ 1 eV, irrespective of the valence state of the samarium. However, an energy shift of about 6 eV is observed for the excitation from the $3p$ level between the divalent and the trivalent samarium. This is explained as arising from the different final states for the $d$ and $p$ core excitation spectra. The strong Hund's-rule coupling for the $4f^7$ final-state configuration overcomes the Coulomb interaction and leads to the nearly identical spectra for the $3d$ core excitations. Atomic total energy calculations using a relativistic, spin-polarized, density-functional Dirac procedure are performed, and the results are in good agreement with the experimental observations.