Effect of crystal potential on dynamic polarizability of negative ions

Summary

We combine a time-dependent approach with a crystal potential model to study environment-specific optical linear response of closed-shell ions within crystals under the influence of an external time-varying field. It is shown how the dynamic dipole polarizability of free halogen anions within the normal dispersion region is altered due to the crystal potentials felt by the anions in environments appropriate for different binary cubic ionic lattices. The pole-positions of the in-crystal anion polarizability are found to be consistent with the vacuum ultraviolet absorption edges of the corresponding alkali halides and to vary linearly with the lattice potentials at the anion sites in these salts. It is observed that the crystal potential induces quite a large enhancement in the anionic absorption oscillator strengths of these dipole transitions, thereby making these values conform well with those of the first excitonic absorptions in such crystals.