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HIGH-RESOLUTION FOURIER-TRANFORM SPECTRA OF THE NO₂ A--X ELCTRONIC BANDS AROUND 1 µm.

J. ORPHAL, S. VOIGT, S. DREHER AND J. P. BURROWS, Institute of Environmental Physics, University of Bremen, P. O. Box 330440, 28334 Bremen, Germany; R. JOST AND A. DELON, Grenoble High Magnetic Field Laboratory, CNRS/MPI, BP 166 X, 38042 Grenoble Cedex 9, France.

The strong vibronic interactions between the A and X electronic states lead to a complex structure of the NO₂ spectrum in the visible and near-IR. The long-wavelength tail of the spectrum is very weak due to small Franck-Condon factors. In 1965, Douglas and Huber recorded the first low-resolution spectra of the NO₂ bands in the near infrared. In 1975, Brand et al. showed that ''hot'' bands are important in this region.

In the past, many high-resolution spectra of NO₂ were recorded, however no rotationally resolved spectra of this important region were reported up to now. We present high-resolution spectra of the first vibronic bands of NO₂ starting around 9740 cm^-1, and discuss vibrational assignments. The dense rotational structure is very difficult to assign, although accurate lower-state energies are available from high-resolution infrared spectra.