Rotational Spectrum of HNO\u3csub\u3e3\u3c/sub\u3e in the v\u3csub\u3e5\u3c/sub\u3e and 2v\u3csub\u3e9\u3c/sub\u3e Vibrational States

The millimeter/submillimeter transitions of the ν5–2ν9interacting bands of HNO3have been measured in the symmetric top limit. Torsional splittings in both vibrational bands have been observed. The 2ν9splitting is due to the torsional motion of H around the NO whereas the ν5splitting is due to the large mixing with 2ν9. An analysis is presented in which a Fermi interaction, 2 sets of 2ν9rotational constants, and one set of ν5rotational constants are used to account for all of the perturbation and torsional splitting observed in the spectrum. The 860 lines used in this analysis are fit to 91 kHz