Abstract: Based on the semi-self-constant-field (semi-SCF) d-orbital model and the complete energy matrix diagonalization procedure (CDP), the optical spectra and g factor of CaF₂:Co²⁺ were explained from the local structure of the impurities. The local structure was shown to have collapse effects, but remain an eight-coordinate cubic symmetry. In addition, the dependence of the g factor on the crystal splitting parameter D_q was discussed by the perturbation method (PTM) and CDP. The third order perturbation formula proposed by Macfarlane was shown to be a good approximation, but its validity became worse with decreasing D_q. At last, the applicability of the g formulae constructed on the basis of CDP and spin Hamiltonian theory, together with the difficulties in the case of orbital degeneration, were discussed.

Key words: crystal field, EPR g factor, optical and magnetic properties