Influence of Covalency on the Mn4+2Eg → 4A2g Emission Energy in Crystals

In this paper we review the spectroscopic properties of the Mn4+ ion (3d(3) electronic configuration) and establish a relationship between the energy of the E-2(g) -> (4)A(2)g emission transition and the covalence of the Mn4+-ligand bonding. A new parameter beta(1) = root(B/B-0)(2) + (C/C-0) ((where (B, C (B-o, C-o) are the Racah parameters of the Mn4+ ions in a crystal (free state), respectively) was recently introduced that allows for establishing a linear relationship between 131 and the energy of the E-2(g) level. This makes it possible to understand the large variation in the energy of the E-2(g) -> (4)A(2g) emission transition that is frequently encountered in the spectroscopy of the Mn4+ ions in solids.