Interpretation of the far-infrared spectrum of Fe2+ in cubic CdTe and ZnS

The main purpose of this article is to report the result of calculations for the low-lying energy states of Fe2+ in CdTe. The analysis is extended to the fairly standard case of Fe2+ in ZnS as a verification of the method and to allow a more direct interpretation of the results. Special attention is paid to the relative energy of the levels, wave functions, and oscillator strengths for the far-infrared transitions. In doing so the crystalline field, spin-orbit interaction, spin-spin interaction, and Jahn-Teller effect are considered by means of perturbation theory and diagonalization of part of the Hamiltonian matrix. The results are found to be in satisfactory agreement with the available experimental information of optical absorption in the infrared and far-infrared spectrum. A comparison is also made with two previous different assignments for the optical transitions; our results are consistent with the earliest of these proposals. Effective values for crystal-field, spin-orbit, and Jahn-Teller parameters are calculated. The final eigenfunctions are tabulated.