Influence of Pressure on the Electron Spin Resonance of Hydrogen Atoms in CaF2

Paramagnetic resonance studies of the resolved hyperfine structure of H and D atoms interstitial in Ca${\mathrm{F}}_2$ have been performed at room temperature at hydrostatic pressures over 10 kbar. The pressure results and previous measurements of temperature dependence can be understood if a local vibrational mode and small amounts of charge transfer are considered.