Spin-Orbit Coupling Parameter forMn2+in RbMnF3

Fine structure observed in the ${}_{}{}^6{}_{}{}^{}A_{1\mathrm{g}}^{}{}_{}{}^{}\mathrm{}\left(S\right)\mathrm{}\to {}_{}{}^4{}_{}{}^{}T_{2\mathrm{g}}^{}{}_{}{}^{}\mathrm{}\left(D\right)\mathrm{}$ band in the absorption spectrum of RbMn${\mathrm{F}}_3$ at 77°K has been assigned to the spin-orbit splitting of the ${}_{}{}^4{}_{}{}^{}T_{2\mathrm{g}}^{}{}_{}{}^{}\mathrm{}\left(D\right)\mathrm{}$ level, and the analysis yields a value of 320 ± 10 ${\mathrm{cm}}^{-1\mathrm{}}$ for the parameter ${\xi }_{3d}$.