Refractive Indices of NaNO2 and Anisotropic Polarizability of NO2-

Abstract

The method of minimum deviation was employed to measure the temperature dependence and the dispersion of principal indices of refraction of NaNO ₂ crystal. Their room temperature values have been found to be n _a =1.3455, n _b =1.4125 and n _c =1.6547. The temperature dependence of the birefringence were measured by a Berek compensator. Slight anomalies were found at the transition point. The anisotropic electronic polarizability of a nitrite ion was calculated from the experimental data of refractive indices based on the point-dipole approximation and has been found to be 2.240, 2.716 and 4.610Å ³ along the a , b and c axis, respectively, at room temperature. It was concluded that the large optical anisotropy in this substance mainly arises from the polarizability anisotropy of the nitrite ion.