Many-electron effects in Lγ2,3x-ray emission spectroscopy of rare-earth elements

The L${\gamma }_2$,3(2${\mathrm{s}}^{\mathrm{-}1}$→4${\mathrm{p}}^{\mathrm{-}1}$) x-ray emission spectra of ${\mathrm{Nd}}_2$ ${\mathrm{O}}_3$ and ${\mathrm{Sm}}_2$ ${\mathrm{O}}_3$ were measured in order to study the strong configuration interaction between a 4p hole level and the double 4d hole 4$f^{(n+1)}$ electron levels. The spectra are calculated also using the Green’s function method. The agreement between theory and experiment is qualitatively good. The spectrum can be interpreted in terms of the spectral function of the final 4p hole where it is shown that the one-electron picture of the 4p hole breaks down due to the strong 4$p^{\mathrm{-}1}$⇆4$d^{\mathrm{-}2}$4$f^{(n+1)}$ super Coster-Kronig process.