Spectra of Hydrogenated Calcium Fluoride Containing Rare-Earth Ions

Abstract

Hydrogenation of calcium fluoride containing rare-earth impurities results in the settlement of ${\mathrm{H}}^{-}$ ions in various lattice positions. The electronic spectra of the rare-earth (RE) impurity ions, infrared absorption due to localized vibration of the ${\mathrm{H}}^{-}$ ions, vibronic spectra of R${\mathrm{E}}^{3+}$ + ${\mathrm{H}}^{-}$ ion pairs, and the electron-spin-resonance (ESR) spectra of these pairs are mutually consistent in yielding the position and symmetry of the ${\mathrm{H}}^{-}$ sites in the lattice. The location of the ${\mathrm{H}}^{-}$ ions depends on the thermal treatment during and after the hydrogenation. This is observed by reversible and irreversible changes in the various spectra. Spectral changes due to isotopic substitution of ${\mathrm{H}}^{-}$ by ${\mathrm{D}}^{-}$ are described and analyzed.