Light scattering by lithium tantalate at room temperature

The room-temperature Raman spectra of LiTa${\mathrm{O}}_3$ for all symmetry phonons are investigated. We make a new assignment of the phonons, which agrees with the selection rules of a $C_3$ symmetry instead of $C_{3v}$, contrary to Kaminow and Johnston's previous work. The oblique phonon dispersions are obtained and turn out to be consistent with our phonon assignments. We obtain also the polariton dispersion curve and, from it, the low-frequency dielectric constant.