Crystal-field analysis ofEu3+doped in cubic yttrium sesquioxide. Application of the electrostatic and angular overlap models

The phenomenological crystal-field parameters of ${\mathrm{Eu}}^{3+}$ in ${\mathrm{Y}}_2$ ${\mathrm{O}}_3$ are determined with reference to previous symmetry assignments obtained for the ${}_{}{}^7{}_{}{}^{}F_J^{}{}_{}{}^{}$ ($J=1\mathrm{} \mathrm{to} 4$) sublevels by laser-induced polarized fluorescence. The crystal-field plus spin-orbit Hamiltonian is diagonalized on the truncated basis containing the lowest ${}_{}{}^7{}_{}{}^{}F$ multiplet of the $f^6$ configuration. The final mean deviation of the experimental and calculated values is equal to 4.8 ${\mathrm{cm}}^{-1\mathrm{}}$. The results are interpreted on the basis of the electrostatic model including point-charge and dipolar contributions. A possible complementary covalency contribution is found by application of the angular overlap model.