Spin-forbidden transitions in the Fe²⁺ion in ZnS crystals

The optical absorption spectrum of Fe 2+ 3d 6 impurity in ZnS crystals has been measured over the wavenumber range from 10500 cm - -20000 cm -1 at temperatures from 6K up to 70K. The positions of centres of gravity of absorption bands, the intensities of optical transitions and their thermal dependences are well described by the crystal field theory. The crystal field parameters obtained are: B=670 cm -1 , C=2870 cm -1 , zeta '= zeta =-335 cm -1 and Delta =-3500 cm -1 .