ROTATIONAL ANALYSIS OF THE 6480 A ABSORPTION OF NO21,2

About 300 rotational transitions in the 6480 A region in the visible absorption of NO//2 gas have been assigned by laser-excited fluorescence. A majority of the stronger transitions belong to the K equals 0 and K equals 1 subbands of a vibronic band, T//0 equals 15434. 9 cm** minus **1, whose upper state is predominantly an a//1 vibrational level of the electronic **2B//2 basis state. Other groups of relatively weaker lines form (i) a severely-perturbed K equals 2 subband attributed to the same series as the K equals 0 and 1 subbands; (ii) a well-developed though relatively weak K equals 3 subband assigned to a hybrid level of mainly **2A//1 character, the transition to this level being induced by vibronic coupling; and (iii) a K equals 6 subband assigned to a parent (i. e. , **2B//2 basis) vibrational level different from that identified at 15435 cm** minus **1. Rotational constants are not well defined and vary considerably from one subband to another; large pseudo-centrifugal distortion constants are attributed to higher-order effects of the vibronic coupling. Frank-Condon analysis of the intensity distribution in fluorescence leads to a tentative vibrational assignment of 160 for the state at 15435 cm** minus **1.