Jahn-Teller effect in the fluorescent level ofMn++in ZnSe and ZnS

Uniaxial-stress experiments have been used to analyze the fine-structure lines of the lowest ${}_{}{}^4{}_{}{}^{}T_1^{}{}_{}{}^{}$ level of ${\mathrm{Mn}}^{++}$ in cubic ZnSe and in cubic ZnS containing stacking faults. We show that the two fine-structure lines due to the cubic centers in ZnSe and ZnS can be interpreted by Ham's model corresponding to a strong Jahn-Teller coupling with $E$ symmetry modes. In both cases, the observed lines correspond to transitions from the $|{}_{}{}^6{}_{}{}^{}A_1^{}{}_{}{}^{}〉$ fundamental state to the almost degenerate states $|{\Gamma }_7〉$, $\left(\frac{3}{\sqrt{10}}\right)\left|{\Gamma }_8\right(\frac{3}{2})〉-(\frac{1}{\sqrt{10}}\left)\right|{\Gamma }_8\left(\frac{5}{2}\right)〉$ for the line at lower energy and $|{\Gamma }_6〉$, $\left(\frac{1}{\sqrt{10}}\right)\left|{\Gamma }_8\right(\frac{3}{2})〉+(\frac{3}{\sqrt{10}}\left)\right|{\Gamma }_8\left(\frac{5}{2}\right)〉$ for the line at higher energy. The influence of the Jahn-Teller effect on the axial ${\mathrm{Mn}}^{++}$ centers in stacking faults of ZnS is also briefly considered. Finally a comparison is made of the Jahn-Teller effect in the lowest ${}_{}{}^4{}_{}{}^{}T_1^{}{}_{}{}^{}$ and ${}_{}{}^4{}_{}{}^{}T_2^{}{}_{}{}^{}$ states of ${\mathrm{Mn}}^{++}$ in ZnS and ZnSe.