Knowledge Bank

Infrared spectrum of deuterated nitrous acid, $DNO2$, has been obtained below $1200cm-1$ with a resolution better than $0.01cm-1$. Two conformers, cis and trans, can be seen in the spectrum. The $\nu 3,\nu 4,\nu 5$ and $\nu 6$ bands of the trans form and the $\nu 4$ band of the cis form have been analyzed rotationally. The $\nu 3$ or $\nu 4$ fundamentals of cis $DNO2$ could not be found in the spectrum. All analyzed fundamentals are pure a type bands, except $\nu 6$ which is a c type band, and they showed no b type structure. Only the $\nu 3$ band of trans $DNO2$ showed signs of some local perturbations. All other fundamentals could be fitted well using Watson's S reduced Hamiltonian. The ground state combination difference data from the infrared spectrum and the previously published microwave data have been used to determine accurately the rotational and quartic centrifugal distortion constants of the ground state for both of the conformers.