Reorientation of Impurity-Fluoride Interstitial Complexes in Rare-Earth-Doped CaF2

Measurements of dipole relaxation by the method of ionic thermocurrents have been made on Ca${\mathrm{F}}_2$: ${\mathrm{Gd}}^{3+}$ and peaks at 140 and 60.5 K have been observed. Analysis yields reorientation energies and ${\tau }_0\text{'}\mathrm{s}$ of 0.395 eV and 1.2 × ${10}^{-13\mathrm{}}$ sec for the upper peak and 0.167 eV and 2 × ${10}^{-13\mathrm{}}$ sec for the lower peak, respectively. Opportunity is taken to correct the previously reported parameters for the low-temperature peak in Ca${\mathrm{F}}_2$: ${\mathrm{Er}}^{3+}$. The correct values are 0.147 eV and 3 × ${10}^{-13\mathrm{}}$ sec.