Optical Absorption Spectrum of Mn2+ in Cubic and Tetragonal Ligand Fields

The fine-line absorption spectra of the Mn2+ ion in MnCl2·6NH3, MnCl2·2H2O, nNH4Cl·MnCl2·2H2O, and KCl·MnCl2·2H2O have been measured at low temperatures. The ion lies at a site of cubic symmetry in the amine and approximate tetragonal symmetry in the hydrates. A cubic ligand field calculation has been made for the d5 configuration which includes spin—orbit coupling and with it level splittings and doublet intensities are discussed. The calculations were further extended to include a tetragonal distortion and were then able to reproduce reasonably well the fine structure in the 4T2 level of the hydrates observed at 27 000 cm−1.