15min:

TERRANCE J. CODD, MING-WEI CHEN, MOURAD ROUDJANE AND TERRY A. MILLER, Laser Spectroscopy Facility, The Ohio State University, Columbus, Ohio 43210.

The A-X spectrum of NO₃ has been previously observed using cavity ringdown spectroscopy (CRDS) by Andrei Deev 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 8700 cm^-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 NO₃ we recently obtained spectra from 7550 cm^-1 to over 10000 cm^-1 using our moderate resolution ( eq 0.05 cm^-1) jet cooled CRDS apparatus. Jet cooling in our apparatus reduces the rotational temperature to <30 K and eliminates vibrational hot bands greatly simplifying the spectrum. We are able to resolve and assign more than 15 vibronic features including a new assignment of the 3¹₀ band. Analysis of the ₄ progression shows weak Jahn-Teller coupling in this mode. Anomalous band contours and anharmonic spacings are observed for the _{1 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.