Low-frequency depolarized light scattering from aqueous solutions of oxo acids and their sodium salts

Abstract

The depolarized scattering profile between 3 and 300 cm^-1 has been studied for aqueous solutions of perchloric acid and nitric acid, and their sodium salts. The profile has been analysed in terms off our component bands, two of which are at zero energy shift, one is at c. 60 cm^-1 and one at c.180 cm^-1. In addition, solutions containing the nitrate ion show evidence for two extra bands which have been assigned to a tunnelling mode of the NO₃^- ion (c. 10 cm^-1) and a cooperative librational mode (c. 120 cm^-1). Changes in half width have been interpreted in terms of a decrease in motional damping due to the presence of foreign species. The intensity of all components shows a considerable change with concentration; this is dependent on ion polarizability. Interpretation of the results in terms of cooperative phenomena in the condensed phase is also discussed.