Reflection spectra of NaClO3, NaBrO3, and LiIO3 gyrotropic crystals in the vacuum UV region

The reflection spectra in the fundamental-absorption region, 5-25 eV (250-40 nm), of optically active crystals with cubic symmetry (NaClO3, NaBrO3) and uniaxial optically active crystal (LiIO3) have been investigated. It is shown that the reflection spectra of cubic crystals have a similar structure, which is determined by the electronic transitions in the XO3 group. The comparison of these spectra with the corresponding spectrum of lithium iodide made it possible to determine the type of transition in the spectra of cubic crystals. Using the projection operator method, it was shown that the sign of optical rotation of cubic crystals with symmetry T is independent of the screw axis sign. Possible reasons for the unprecedentedy large optical rotation of lithium iodide crystal in the optical axis direction are considered.