Effects of vibrational optical activity in the reflection spectra of crystals for the frequency regions of nondegenerate vibrations

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Abstract
A new method for studying crystal gyrotropy by reflection vibrational spectra is proposed. The gyrotropy, connected with the dipole-active nondegenerate vibrations, excites a reflected wave polarized normal to the incident wave. This phenomenon is called in this paper reflection nondegenerate vibrational optical activity. Despite the existence of birefringence, the intensity of this wave provides information about the gyration tensor and about the frequencies of the nondegenerate vibrations. A Fresnel-type boundary problem has been solved for reflection and refraction at the air–birefringent-gyrotropic-crystal boundary. The dielectric permittivity tensor near the optically active nondegenerate vibrations has been obtained, and the selection rules at the manifestation of these vibrations in the above-mentioned phenomenon have been found. The peculiarities of the same phenomenon and of the normal electro-magnetic waves in different classes of biaxial and uniaxial crystals have been studied.