EPR AND OPTICAL-PROPERTIES OF IMPURITY CENTERS IN LOW-SYMMETRY CRYSTALS

Representative examples of low-symmetry materials containing color centers are discussed. The reduction in symmetry from the fully octahedral symmetry of the alkali halides induces a wide range of effects, including the lifting of electronic and vibrational degeneracies, the occurrence of spin-forbidden transitions, and highly anisotropic g- and hyperfine-tensors, and these are discussed in appropriate sections. Special consideration is given to halides, sulfates, Tutton salts, double sulfates and nitrates, phosphates, arsenates, molybdates, vanadates, acetates, tartrates, oxalates and formates.