Vibrational Spectra of Isotopic Nitric Acids

Abstract

The vibrational spectra of four isotopic nitric acid molecules including the ¹⁵N and D species have been obtained in the vapor and solid phases. The Raman spectra of anhydrous and wet normal nitric acid were also studied. Previous assignment of the fundamental modes has been revised, and the spectra in the three phases have been correlated. The potential barrier against internal rotation of the hydroxyl group has been calculated to be 7.8±0.1 kcal/mole in both the H and D acids. A set of least‐squares fitted valence force constants which reproduce the observed fundamentals with an average error of 0.6% has been derived.