The effect of excited configurations 3d54p, 3d54d, and 3d54fon the crystal field levelsGgr;3andGgr;5of tetrahedral and octahedral Fe2plus;ion via crystal field interaction has been discussed. The shift of theGgr;3andGgr;5levels due to configuration interaction has been estimated in the two cases within the framework of crystal field model carrying out the perturbation calculation up to second order and using Slater functions for the radial integrals. Such calculation shows that in the case of tetrahedral Fe2plus;ion in ZnS, the net effect of the excited configurations 3d54p, 3d54d, and 3d54fon the crystal field spectra is to close up the levelsGgr;5andGgr;3by an appreciable amount of about 1000 cmminus;1and the major part of the contribution comes from 3d54p. In the octahedral case also (Fe2plus;in MgO), the effect arising from 3d44donly is not negligible although comparatively smaller, the separationlpar;Ggr;3minus;Ggr;5rpar;is narrowed by about 380 cmminus;1.
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