The Spin-Forbidden Absorption Spectrum of Fe²⁺ in Gs₃FeCl₅ Crystal

According to analysis observed absorption spectra of Fe²⁺ ion in the Cs₃FeCl₅ crystal, the present article has suggested that Fe²⁺ ion is located at distorted tetrahedral C₂, lower symmetry crystal site in the Cs₃FeCl₅ crystal. By using a simplifed strong-field scheme of block quasi-diagonal form, the strong-field matrices of C₂, （d⁶） have been derived. By suitably selecting the parameters, the complete energy spectra of spin triplet state have been calculted. Theoretical values of absorption spectra are in good agreement with experimental observation. And, splitting of ground state is good agreement with our calculation. Thus, we have not only explained observed absorption spectra, but also determined that Fe²⁺ in FeCl₄^2- complex could be located at C₂, symmetry site of tetrahedral in the Cs₃FeCl₅ crystal.