Raman Effect in Ferroelectric Sodium Nitrite Crystal. II. Dependence of B2 Type Phonon Spectrum on Propagation Direction

Abstract

Abstract The Raman spectra corresponding to the (bc) component (B2 type vibrations) of the polarizability tensor in the ferroelectric sodium nitrite crystal (C2v20) have been observed with various directions of the phonon propagation. It has been found that one of the B2 Raman lines at 160 cm−1 splits into two components when the phonon propagates in a direction 45° from the c axis in the ac plane. This splitting has been ascribed to an interaction of a B2 and B1 type lattice-vibrations whose frequencies are accidentally equal to each other in the phonon propagation direction now in question.