Jahn-Teller Splittings in the Optical Absorption Spectra of Divalent Iron in Cadmium-Chloride-Type Crystals

Measurements of the Jahn-Teller splittings of the ${}_{}{}^5{}_{}{}^{}T_{2g}^{}{}_{}{}^{}\left({}_{}{}^5{}_{}{}^{}D\right)\to {}_{}{}^5{}_{}{}^{}E_g^{}{}_{}{}^{}\left({}_{}{}^5{}_{}{}^{}D\right)$ optical transition of divalent iron in the near infrared are reported for Cd${\mathrm{Cl}}_2$, Cd${\mathrm{Br}}_2$, Mg${\mathrm{Cl}}_2$, and Mn${\mathrm{Cl}}_2$ crystals containing about 15% divalent iron and for ferrous chloride. The variation of the magnitude of the observed splittings with temperature for the various host crystals is discussed and compared with theoretical predictions.