Knowledge Bank

The $A~$-$X~$ spectrum of NO$3$ has been previously observed using cavity ringdown spectroscopy (CRDS) by Andrei Deev \emph{et. al} under ambient conditions. There the authors assigned a number of vibronic bands in the spectrum. However, under these conditions, hot-bands may be present and the spectrum becomes very congested at frequencies higher than $\sim$8700cm$^{-1}$ due to the density of vibronic states and the overlap of their rotational contours. In order to obtain more information about the $A~$ state of NO$3$ we recently obtained spectra from 7550 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ to over 10000 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ using our moderate resolution ($\simeq$ 0.05 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$) jet cooled CRDS apparatus. Jet cooling in our apparatus reduces the rotational temperature to $&lt;$30Kandeliminatesvibrationalhotbandsgreatlysimplifyingthespectrum.Weareabletoresolveandassignmorethan15vibronicfeaturesincludinganewassignmentofthe3$^{1}_0$ band. Analysis of the $\nu 4$ progression shows weak Jahn-Teller coupling in this mode. Anomalous band contours and anharmonic spacings are observed for the $\nu 1$$\nu 4$ combination bands and the cause is being investigated. We also see some features that could belong to vibronically forbidden transitions which may be magnetic dipole allowed.