Knowledge Bank

Millen and $Morton1$ have calculated the structure of nitric acid from the microwave spectra of three isotopic species. In order to refine this structure, the microwave spectra of the singly substituted oxygen-18 species of nitric acid have been studied. Many transitions have been assigned and accurate rotational constants have been determined for all three species. Since the nitrogen atom lies close to the center of mass of the molecule, the microwave spectra of certain doubly substituted species of nitric acid have also been studied in an effort to improve the location of the nitrogen atom in the principal axis system. The structural parameters of nitric acid will be discussed. $\mathrm{<mrow\; data-mjx-texclass="ORD">\ast </mrow>}$This research was made possible by support extended to Harvard University by the Office of Naval Research. $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ D. J. Millen and J. R. Morton, J. Chem. Soc. 1523 (1960).