Cluster Model For Radiative Transition Probabilities Of D(5) Ions In Tetrahedral Symmetry: Case Of Mn2+ In The Common Cation Series Zns, Znse, And Znte

A cluster model is proposed to account for the increase of one to almost two orders of magnitude for the radiative transition probabilities (RTP's) of Mn2+ in the common cation series ZnS, ZnSe, and ZnTe. First, it is shown that the RTP's of d(5) ions in tetrahedral symmetry are given by second-order perturbation schemes involving the molecular electric dipole moment and the molecular spin-orbit (MSO) interaction. Then, a model is elaborated to calculate the monoelectronic matrix elements of the molecular electric dipole moment and of the MSO interaction. In particular, three methods are proposed to calculate the molecular electric dipole moment. For the studied compounds, the metal-metal, metal-ligand, and ligand-ligand contributions of the group overlaps to the molecular electric dipole moment and to the MSO interaction are analyzed. It is shown that the strong increase of the RTP's when passing from ligands S to ligands Se and Te is primarily controlled by the MSO interaction of the ligands. Then, the radiative lifetimes (RL) for Mn2+ in ZnS, ZnSe, and ZnTe, are calculated and found to be in good agreement with the experimental values. Finally, the RL's of Mn2+ in other II-VI compounds, and of Mn2+ and Fe3+ in several III-V compounds are briefly considered.