The eighth-order perturbation formula for the EPR cubic zero-field splitting parameter of d 5 ( 6 S) ion and its applications to MgO:Mn 2+ and MnCl 2 .2H 2 O

The eighth-order perturbation formula for the EPR cubic field splitting parameter alpha has been obtained by taking a cubic crystal field and the spin-orbit interaction as the perturbation Hamiltonian. In the calculation, not only spin quartet states but also spin doublet states have been considered. The calculated result shows that the contributions of the double states and eighth-order perturbation cannot be neglected. For MgO:Mn 2+ and MnCl 2 .2H 2 O, the d-d transitions and the cubic zero-field splitting parameter have been calculated by using Zhao's self-consistent-field (SCF) orbital for the Mn 2+ ion and the high-order perturbation formula for the cubic zero-field splitting parameter have been obtained. The results of applications agree well with experiments.