ROTATIONAL QUANTUM NUMBER AND VIBRONIC SYMMETRY OF NO2 EXCITED WITH VISIBLE-LIGHT IN THE REGION OF 563-566-NM - OPTICAL-OPTICAL DOUBLE-RESONANCE MEASUREMENT AND SPIN-ORBIT INTERACTION BETWEEN (2)B(2) AND (2)A(2) VIBRONIC STATES

An optical-optical double resonance (OODR) technique has been employed to determine the rotational quantum number and vibronic symmetry of NO2 in the region of 563-566 nm. The first excitation step corresponds to the intermediate B-2(2)<--X2A1(0,0,0) transition of a parallel type. The lowest rotational levels are identical with those of the 17 713.203-cm-1 vibronic band reported by Delon et al. from their jet-cooled LIF experiment [J. Chem. Phys. 1991, 95, 5701]. The intermediate state is an admixture of two vibronic states, B-2(2) (vibronically-mixed states between al vibrational levels on AB-2(2) and b2 vibrational levels on X2A1) and 2A2 (a1 vibrational levels on C2A2), being coupled through spin-orbit interaction. The second excitation step corresponds to the final 2B-2(2)(0,0,0)<--intermediate 2A2 transition of a perpendicular type, the analysis of which provides information on the C2A2 state: the vibronic origin T(v) approximately 17 709 cm-1, the bond length r(N-O) approximately 0.134 nm, and the bond angle theta approximately 109-degrees. The vibronic level detected in this OODR study could be assigned to either C2A2(0,2,0) or C2A2(1,0,0).