On Birefringence of NaNO₂ and NaNO₃ and on Anisotropy of Electronic Polarizabilities of NO₂ and NO₃ Radicals

Abstract

The birefringences of NaNO₂ and NaNO₃ have been discussed by taking account of the dipole interaction among the Na-ions and the NO₂-radicals or NO₃-radicals. From the condition necessary to explain the birefringence the electronic polarizabilities of these radicals are obtained. The radicals have generally the anisotropic polarizabilities. It seems valid to attribute this property to the anisotropy of the N–O bond. Among the various models, it can be concluded that the model based upon the bonds is more suitable than that of the dipole model within the region of the radicals. Discussion about the birefringence by comparing with that of CaCO₃ is also made.