Jahn-Teller effect and optical properties of ZnSe:Fe²⁺

Zeroth-order vibronic wave functions are built in the Born-Oppenheimer limit as symmetrized products of electronic functions and vibronic functions corresponding to up to N vibrational quanta. A linear Jahn-Teller Hamiltonian is then added to the spin-orbit and static crystal-field contributions which are taken as fixed parameters in accordance with their established properties. The diagonalization of the whole Hamiltonian predicts the energies and intensities of the absorbed lines which are then compared with the spectra. Good agreement with experiment is obtained when the energy of the coupling phonon h{stroke}ω is 65 cm^-1 (good correspondence with the lattice dynamics of ZnSe) and the Jahn-Teller energy E_JT is 230 cm^-1 (in the same range of the reported values for ZnS:Fe²⁺ and CdTe:Fe²⁺). A very important point of the discussion is the stability of the reached solution with respect to _N the maximum number of vibrational quanta considered in defining vibronic functions. It is found that good stability is reached for N ≥ 8. The values of h{stroke}ω and H_JT reported above correspond to the case N = 10.