4fn→4fn−15dSpectra of Rare-Earth Ions in Crystals

Abstract

The $4f^n\to 4f^{n-1\mathrm{}}5d$ absorption spectra of rare-earth ions, R${\mathrm{E}}^{2+}$ or R${\mathrm{E}}^{3+}$, in crystals can be fitted with energy gaps in the ground multiplets of the $4f^{n-1\mathrm{}}$ core. Unlike the shielded $4f^n$ configuration, the $4f^{n-1\mathrm{}}5d$ levels of RE in crystals are therefore very different from those of free ions, and are formed through the interaction between the electron in $5d$ orbitals with the $4f^{n-1\mathrm{}}$ core.