15min:

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 ( ₃ and ₄ 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 20 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 ₃ and ₄ and possible bilinear coupling between the totally symmetric stretch, ₁, and ₄. We conclude that the JT coupling in ₄ is quite weak. Satisfactory spectral fits can be obtained assuming weak JT coupling for ₃ also, though there is some evidence of strong JT coupling for ₃ and the strengths and weaknesses of each case are discussed.