Absorption and magnetic circular dichroism of the vibronically allowed d-d transitions in Mn²⁺: CdF₂

The absorption spectrum at room temperature and liquid helium temperature and the magnetic circular dichroism (MCD) spectrum at liquid helium temperature are reported for ˜ 15 per cent Mn²⁺ in CdF_2` The results indicate that even at these concentrations the Mn²⁺ ions occupy undistorted cubal symmetry sites. The intensity is entirely vibronic with at least one t_1U vibration of 155 cm^-1 active. Crystal-field calculations have been used to assign the gross features of the spectrum and the use of MCD has allowed an almost complete elucidation of the fine structure observed. In the two⁴T_2g states this structure is assigned to the various spin orbit components. The MCD results indicate that vibronic mixing to the ground state, rather than to excited states, produces the observed spectrum and that both⁴T_1Uand⁴ T_2U states probably mix.