Knowledge Bank

Extensive measurements of the rotational spectrum of nitric acid $(HNO3)$ in its $\nu 5$ excited vibrational state have been carried out in the millimeter and submillimeter wave spectral region. The assignment of this spectrum was significantly aided by the recent infrared work of Maki and $Wells1$. Much of the data was obtained on a new broadband millimeter and submillimeter spectrometer which is based on traveling wave tube and harmonic generator technology. The long, continuous survey sweeps allowed by this system greatly aided the assignment of the relatively weak excited state features from the very dense background spectra of the ground and lower lying excited states.