An EPR Theory for d~4(D_2d)Ions and a Study of the Optical and Magnetic Properties of ZnS:Cr²⁺

Analyses were given to the optical and EPR spectrum of ZnS:Cr²⁺. An unified calculation was given to the fine structure of the spin-allowed bands, the ground state zero-field splitting, the Zeeman splitting and the EPR g factors, by the complete configuration mixing EPR theory for d(D_2d) systems. The results showed that the effective crystal field surrounding the Cr²⁺ ions is of octahedral rather than tetrahedral symmetry as reported by all previous works.