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 ⁴T1g(⁴F) cubic-field ground term are observed with frequencies of 235, 499, 923, 953, and 1088 cm^-1 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 d³ configuration parameter values for the cadmium-chloride crystals with 2.5-wt% cobalt are (in cm^-1) Dq=-670, $B=790$, $C=3320$, ζ=-512, ζ^'=-513, $v=57$, and v^'=-345. EPR measurements on the cadimum-bromide crystals with 0.1-wt% cobalt yield new values of g_∥=3.74±0.1 and g_⊥=4.67±0.1 which resolve difficulties in fitting the experimental data for this crystal. Raman lines were also observed for antiferromagnetically ordered CoCl₂.