Breakdown of the one electron approximation for 4p core electron energy loss spectra in the rare earths

At high incident electron energies the 4p core electron energy loss features of clean La, Ce and Gd strongly resemble the corresponding XPS spectrum with evidence of strong 4p^-1 ? 4d^-2?f giant Coster-Kronig resonance in the “4p_{$\text{1}\text{2}$}” spectrum. The absence of charge transfer screening peaks in the $\text{4p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ loss of the oxides is attributed to localised 4p → 5d¹ excitation. As the primary energy approaches threshold, a satellite on the low energy side of the $\text{4p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ losses of La and Ce grows in intensity, due to excitations of multiples through non-dipole transitions.