Optical spectroscopy of Mn2+ ions in solid solution and Suzuki phase in NaCl single crystals

The optical spectroscopy of Mn2+ ions both in dipolar form and forming Suzuki-phase precipitates has been studied in NaCl by photostimulated luminescence at room and liquid nitrogen temperatures. An analysis of the positions of the crystal field transitions shows that the 10 Dq value is slightly higher (about 7%) in the Suzuki than in the dipolar phase while the covalency is the same in both cases. Such analysis allows us to estimate the value fσ−fπ=4.8% from the optical data which is in agreement with the EPR data for [MnCl6]4− clusters. Moreover, an intense band peaking at 231 nm which disappears when the dipolar phase is formed has been ascertained to be associated with the Suzuki phase. This band has been assigned to the double excitation 6A1(S) +6A1(S) → 4T1(G)+[4A1(G), 4E(G)]; that is consistent with the existence of Mn2+ ions in close positions in the Suzuki phase.