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ON THE HYPERFINE STRUCTURE OF NO₂ LEVELS NEAR DISSOCIATION THRESHOLD.

JU XIN AND SCOTT A. REID, Department of Chemistry, Marquette University, Milwaukee, WI 53201-1881.

We report the application of polarization quantum beat spectroscopy (QBS) to probe the hyperfine structure of single NO₂ molecular eigenstates in the region 2.5 cm^-1 below dissociation threshold (D₀=25128.57 cm^-1). The hyperfine interaction is substantially weaker than that found at energies below 22~000 cm^-1, but is similar on average to that observed 50-100 cm^-1 below threshold. The ratio of J=3/2 to J=1/2 levels is much larger than that expected on the basis of complete rovibronic mixing, but is consistent with a previous study.