Jahn-Teller effect in the luminescence spectra of ZnS:V⁺ and ZnSe:V⁺

The infrared emission spectra of ZnS:V+ and ZnSe:V+ are reported examining temperature dependence. The unusually rich spectra are theoretically explained by assuming a vibronic coupling due to ε modes. A diagonalization of the Hamiltonian matrix is performed using wave functions constructed in the Born-Oppenheimer limit. The Jahn-Teller energy is the only adjustable parameter. When this parameter is about 80 cm−1 for ZnS:V+ and 65 cm−1 for ZnSe:V+ good agreement between theory and experiment is found and the main features of the spectra for both systems are explained. The frequencies of the coupling modes are taken close to the TA(L) modes

Infrared luminescence and application of a vibronic-coupling Hamiltonian to the level structure of CdTe:Fe²⁺

Samples of crystalline CdTe doped with two different concentrations of iron were prepared by the vertical high-pressure Bridgman method. Absorption and emission spectra were recorded at liquid-helium temperature in the region of the 5T2(D)? 5E(D) infrared transitions of substitutional Fe2+(d6) ions. Especially in the range between 2200 and 2300 cm−1, a rich structure is resolved comprising more lines than predicted from plain crystal-field theory. The explanation of all the important lines is found after introducing a vibronic Jahn-Teller term to the Hamiltonian. A linear coupling between the double-degenerate vibrational mode ε (or γ3) to the electronic orbitals of the atomic multiplet of symmetry 5D leads to the diagonalization of the total Hamiltonian in a set of vibronic functions. Just one free parameter is used in the adjustment: the so-called Jahn-Teller energy representing the strength of the coupling. The corresponding value that we report here is 3 cm−1. The energies thus found are in good agreement with the positions of the observed lines in the spectra. With the final wave functions we can calculate the relative intensities of the most important transitions and approximate theoretical line shape. This is also in good agreement with the experiment. Using these same energies and wave functions a calculation was performed to explain data existing in the literature about far-infrared absorption for the system CdTe:Fe2+. Again, good agreement between experiment and theory is found