15min:

MING-WEI CHEN, TERRANCE J. CODD, GABRIEL M. P. JUST AND TERRY A. MILLER, Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210.

The 0⁰₀, 4¹₀, 4²₀ and 2¹₀ vibronic bands of the A state NO₃ absorption spectrum has been successfully observed with our high-resolution, jet-cooled cavity ring-down apparatus. Ground state combination differences\footnoteK. Kawaguchi, E. Hirota, T. Ishiwata, and I. Tanaka, J. Chem. Phys. , \underline\textbf93, 951 (1990)\footnoteK. Kawaguchi, T. Ishiwata, E. Hirota, and I. Tanaka, Chem. Phys. , \underline\textbf231, 193 (1998) are used to analyze all four vibronic bands. Rotational transitions of the 4¹₀ band (parallel band) band are assigned including some levels that appear to be doubled. The 4²₀ band verifies the existence of anomalous doublets in both the 4¹₀ and 4²₀ bands. The 2¹₀ band is a perpendicular band which has a different band type. Preliminary assignments of this band are utilized for the comprehensive understanding of the structure of NO₃ in the A state. Besides the ₂ and ₄ vibronic bands, the vibronically forbidden origin band (0⁰₀ band) has also been recorded. The weakly observed A-X origin band structure appears to be different from either the parallel or perpendicular band type and is likely a magnetic dipole transition.