STRONG AND VERY STRONG COVALENCY EFFECTS ON THE LIFETIME OF MN-2+ IN II-VI COMPOUNDS

A ligand field model is proposed for the radiative lifetimes or dipole strengths of d5 ions in tetrahedral symmetry. The dipole strength of the transition from the fluorescent orbital triplet state 4T1 to the ground state 6A1 is given by second-order perturbation schemes involving the dipole moments and the molecular spin-orbit interactions for the electrons of the metal and of the ligands. In the case of Mn2+ in ZnS, ZnSe and ZnTe, it is shown that the multielectronic wave functions 4T1 and 6A1 have approximately the same degree of covalency and that the dominant operator governing the lifetimes of Mn2+ is the spin-orbit interaction of the p-electrons of the ligands.