Abstract: Under the ligand field approximation, the Hamilton matrix of FeCl₅^3-(O_kSymmetry) and other similar ions can be cut apart with irreducible tensor method. The method is simple in calculating charge transfer (CT) spectra. In calculating, theis used as a base vector, the Coulomb interaction and spin-orbital interaction are considered, the Coulomb interaction between different electron configurations is neglected, and frozen orbital approximation is taken. The calculated results are in agreement with those from experiments.

Key words: CT spectra, Irreducible tensor method, Octahedral point group