Optical and spin resonance properties have been calculated for the self trapped hole (Vk centre) in CaF2, SrF2 and BaF2. The electronic properties are regarded as those of an F2- molecular ion whose internuclear spacing has been changed by the crystalline environment, and evidence is given that this is a good approximation. The spacing is obtained from a detailed lattice relaxation calculation allowing motion of many neighbours to the defect. The results are not sensitive to the different interatomic potentials used. Good agreement with experiment is obtained for optical transition energies and linewidths and for spin resonance parameters
