Effects of uniaxial stress and electric fields on localized vibrational modes of H - and D - ions in CaF 2

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 CaF 2 . Electric dipole transitions are allowed from the singlet Γ 1 ground state to the triply degenerate Γ 5 excited states and the absorption lines are sufficiently narrow at low temperatures ( ca . 1 cm -1 ) to enable splitting of the Γ 5 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 Γ 3 and Γ 1 levels, which cannot be observed in unperturbed crystals, have been found in stressed crystals due to stress induced admixture of the nearby second harmonic Γ 5 state.