Jahn-Teller effect in theT22state ofCu2+in ZnS

Abstract

The narrow lines at 6927 and 6913 ${\mathrm{cm}}^{-1\mathrm{}}$ in emission spectra of ${\mathrm{Cu}}^{2+}$ in cubic ZnS are attributed to the ${}_{}{}^2{}_{}{}^{}E\to {\Gamma }_7\left({}_{}{}^2{}_{}{}^{}T_2^{}{}_{}{}^{}\right)$ and ${}_{}{}^2{}_{}{}^{}E\to {\Gamma }_8\left({}_{}{}^2{}_{}{}^{}T_2^{}{}_{}{}^{}\right)$ transitions. The splitting of the ${}_{}{}^2{}_{}{}^{}T_2^{}{}_{}{}^{}$ level and the $g\left({\Gamma }_7\right)$ gyromagnetic factor are interpreted as being due to a dynamic Jahn-Teller effect in the ground state ${}_{}{}^2{}_{}{}^{}T_2^{}{}_{}{}^{}$. The coupling occurs with $E$ optical phonons with $S_E=\frac{E_{\mathrm{JT}}}{\hslash \omega }\simeq 3$. It is essential to consider the effect of ${}_{}{}^2{}_{}{}^{}E$ excited state to explain simultaneously the ${}_{}{}^2{}_{}{}^{}T_2^{}{}_{}{}^{}$ splitting and $g\left({\Gamma }_7\right)$. The ratio between the emission-lines intensities is in agreement with this model.