Electronic Raman spectra of divalent cobalt ions in cadmium-chloride—type crystals

The polarized Raman spectra of divalent cobalt ions at concentrations ranging from 2.5 to 10 wt% in cadmium chloride, cadmium bromide, manganese chloride, and cobalt chloride from 15 to 300°K are reported. All five electronic transitions between the spin-orbit and trigonal crystal-field-split levels of the ${}_{}{}^4{}_{}{}^{}T_{1g}^{}{}_{}{}^{}\left({}_{}{}^4{}_{}{}^{}F\right)$ cubic-field ground term are observed with frequencies of 235, 499, 923, 953, and 1088 ${\mathrm{cm}}^{-1\mathrm{}}$ for cadmium-chloride crystals containing 2.5-wt% cobalt. The strong-field matrices of the trigonal crystal field and the Zeeman interaction are calculated and quantitatively explain the experimental data. The $d^3$ configuration parameter values for the cadmium-chloride crystals with 2.5-wt% cobalt are (in ${\mathrm{cm}}^{-1\mathrm{}}$) $Dq=-670\mathrm{}$, $B=790\mathrm{}$, $C=3320\mathrm{}$, $\zeta =-512\mathrm{}$, ${\zeta }^{\prime }=-513\mathrm{}$, $v=57\mathrm{}$, and $v^{\prime }=-345\mathrm{}$. EPR measurements on the cadimum-bromide crystals with 0.1-wt% cobalt yield new values of $g_{\parallel }=3.74\mathrm{}\pm 0.1$ and $g_{\perp }=4.67\mathrm{}\pm 0.1$ which resolve difficulties in fitting the experimental data for this crystal. Raman lines were also observed for antiferromagnetically ordered Co${\mathrm{Cl}}_2$.