Experimental and Theoretical Study of the Low-Lying Energy-Level Structure ofSm3+in CaF2

Abstract

The optical spectrum exhibited by the ${\mathrm{Sm}}^{3+}$ ion in Ca${\mathrm{F}}_{2}$ is analyzed assuming both octahedral and trigonal site symmetries. Calculations were performed using a tensor operator technique in the complete intermediate-coupling scheme. The crystal field parameters and the root-mean-square (rms) deviations obtained are ${B}^{(4)}=\ensuremath{-}906$ ${\mathrm{cm}}^{\ensuremath{-}1}$ and ${B}^{(6)}=618$ ${\mathrm{cm}}^{\ensuremath{-}1}$ with rms deviations of 48.1 ${\mathrm{cm}}^{\ensuremath{-}1}$ for the octahedral site symmetry; ${B}_{0}^{(2)}=118$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${B}_{0}^{(4)}=\ensuremath{-}272$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${B}_{3}^{(4)}=\ensuremath{-}296$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${B}_{0}^{(6)}=38$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${B}_{4}^{(6)}=\ensuremath{-}128$ ${\mathrm{cm}}^{\ensuremath{-}1}$, and ${B}_{6}^{(6)}=1556$ ${\mathrm{cm}}^{\ensuremath{-}1}$, with rms deviation of 35.4 ${\mathrm{cm}}^{\ensuremath{-}1}$ for the trigonal site symmetry. It is suggested that the sample on which the measurements were carried out contains ${\mathrm{Sm}}^{3+}$ ions occupying both octahedral and trigonal symmetry sites. It is also shown that crystal field theory with a single set of ${B}_{q}^{(k)}$ parameters is quite adequate to describe the energy levels lying below 11 000 ${\mathrm{cm}}^{\ensuremath{-}1}$, above which a fairly large energy gap follows.