Jahn–Teller effect on the [TiF 4F 4F int] 6−(C 4v) and [NiF 4F 4F int] 7−(C 4v) clusters embedded into SrF 2 crystals

Abstract

By means of EPR method the associative [TiF 4F 4F int] 6−(C 4v) and [NiF 4F 4F int] 7−(C 4v) centers were revealed in the fluorite type SrF 2:Ti and SrF 2:Ni crystals grown by Bridgman method in helium atmosphere containing some amount of a fluorine gas. It was found that at low temperatures the local structures of these associative centers were exposed to a static rhombic distortion. The reasons of such distortions were accounted for by the assumption that the E ⊗ ( b 1 + b 2) vibronic interaction became effective due to that the ground orbital states of the [TiF 4F 4F int] 6−(C 4v) and [NiF 4F 4F int] 7−(C 4v) centers occurred to be doubly degenerated.