The rotational structure of bands of NO 2 vapor in the region 8300-9000 Å has been partially analyzed and the absorption assigned to the (000)-(000) and (000)-(010) vibronic bands of the Ã2B 2 ← X∼2A 1 electronic transition. Irregular weak perturbations in the N-structure of the upper-state manifold are accompanied by larger resonance-type crossings in the K-structure. The larger perturbation is attributed to vibronic coupling between the Ã state and excited vibrational levels of the ground state, characterized by a low density of ground state levels and a large vibronic coupling matrix element between the Ã and X∼ states. The reconstituted, deperturbed bands have blue-degraded N-structure and strongly red-degraded K-structure, indicating that the bond angle decreases sharply in the excited state. The physical structure of the 2B2 state is uncertain but some suggestions are made. The electronic energy of the 2B2 state is T0 = 11 962.9 cm -1.