Effects of uniaxial stress and electric fields on localized vibrational modes of H- and D- ions in CaF2

Abstract

Abstract This paper contains a description of the effects of stress and electric fields on the fundamental and second harmonic localized vibrational levels of H- and D- ions in CaF2. Electric dipole transitions are allowed from the singlet Γ1 ground state to the triply degenerate Γ5 excited states and the absorption lines are sufficiently narrow at low temperatures (ca. 1 cm-1) to enable splitting of the Γ5 states by the external perturbations to be measured. The measured splittings are a factor of approximately √2 smaller for D- ions than for H- ions. Transitions to the second harmonic Γ3 and Γ1 levels, which cannot be observed in unperturbed crystals, have been found in stressed crystals due to stress induced admixture of the nearby second harmonic Γ5 state.