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

The nitrate radical is a key reactant in atmospheric chemistry leading to the formation of acid rain and is the primary oxidant in the night sky. The A2 E'' state of NO3 is doubly degenerate and is therefore subject to Jahn-Teller (JT) coupling through the degenerate in-plane stretch and bend modes ( nu3 and nu4 respectively). We have taken a moderate resolution CRDS spectrum of the A2 E''-X2 A2' transition of the NO3 radical under jet-cooled conditions. We resolve sim20 vibronic transitions and are able to assign many using an independent anharmonic oscillator model as was presented previously. In order to gain a deeper understanding of the nature of the JT effect in this electronic state we have performed a vibronic analysis including linear and quadratic JT coupling terms for nu3 and nu4 and possible bilinear coupling between the totally symmetric stretch, nu1, and nu4. We conclude that the JT coupling in nu4 is quite weak. Satisfactory spectral fits can be obtained assuming weak JT coupling for nu3 also, though there is some evidence of strong JT coupling for nu3 and the strengths and weaknesses of each case are discussed.