TEMPERATURE DEPENDENCE OF HYPERFINE INTERACTIONS OF HYDROGEN ATOMS IN ALKALINE EARTH FLUORIDES

Detailed measurements as a function of temperature from 77° K to 400° K have been made of the proton and fluorine hyperfine coupling of substitutional and interstitial hydrogen atoms in CaF2, SrF 2 and BaF2. The results are discussed in terms of the bonding of the hydrogen atoms. They are ascribed to a temperaturedependent admixture of charge transfer states in which an electron is excited from fluorine 2s orbitals on to the hydrogen atom.