Electron-excited3dhole states ofLa3+in solids

The ${\mathrm{La}}^{3+}$ excited states with a $3d$ inner hole are investigated by x-ray absorption spectroscopy (XAS), electron-stimulated x-ray emission spectroscopy (EXES), and characteristic isochromat spectroscopy (CIS). The relative energies of these various states are determined and their decay processes are considered. It is shown that the levels associated with the ${\mathrm{La}}^{3+}$ $3d^{9}4f^1$ configuration are well described in $\mathrm{jj}$ coupling. It is shown that the $3d^{9}4f^1$ configuration states decay by direct recombination of the excited electron and the inner hole and simultaneously by transitions taking place in the presence of the extra $4f$ electron. The emissions already observed by Liefeld et al. close to the $3d_{\frac{3}{2}}$ and $3d_{\frac{5}{2}}$ thresholds are studied and interpreted as $f-d$ discrete emissions from $J$ levels of the $3d^{9}4f^2$ configuration. A nonradiative transition from $J$ levels of this same configuration is also evidenced by CIS at the $3d_{\frac{3}{2}}$ threshold; it is identified as a $3d_{\frac{3}{2}}^{-1\mathrm{}}4f^2\to 3d_{\frac{5}{2}}^{-1\mathrm{}}4f^1$ Coster-Kronig-type process. The various nonradiative processes transferring a $3d_{\frac{3}{2}}$ hole to a $3d_{\frac{5}{2}}$ hole are considered and their relative intensity discussed. From all of the results it is concluded that final-state-type coupling effects are weak in the radiative decay of $3d^{-1\mathrm{}}$ excited states in ${\mathrm{La}}^{3+}$.