OBLIQUE PHONONS IN RAMAN-SCATTERING AND IR REFLECTION OF TEO2 CRYSTAL

The Raman scattering and IR reflectivity have been investigated for di fferent crystal configurations. The contours of reflectivity spectra h ave been calculated. The angle dependence of polar vibrational modes i n both reflectivity and Raman spectra have been investigated. The pecu lliarities of the transition from longitudinal mode to transverse one and vice versa both with and without changing of symmetry have been ob tained. The phonon parameters and effective ionic charges of the anion s and cations have been determined. It has been shown that there exist s an effective ionic charge anisotropy of the oxygen and tellurium ion s.