Recent state-resolved investigations of unimolecular dissociation and collisional relaxation of NO, at chemically significant internal energies are outlined. Two powerful double-resonance techniques are described which permit the investigation of these processes on a quantum-state-resolved level of detail. A sequential optical double-resonance technique with sensitive laser-induced fluorescence detection has been employed for assignments of the molecular eigenstates of NO, in the energy range at 17 700 cm-'. Subsequently, we were able to measure state-to-state rotational and vibrational energy transfer in NO,-NO, self-collisions using a time-resolved doubleresonance technique. From these data, direct information about propensity rules and intermolecular interactions for rotational and vibrational energy transfer in NO, self-collisions at high vibrational excitation could be obtained. In addition, we have used a folded high-resolution V-type doubleresonance technique in a free jet to access and to assign rovibronic states of NO, above and below the dissociation threshold, E , . From the doubleresonance spectra, linewidths at around 25 130 cm-' as a function of internal energy, E, and total angular momentum, J , could be extracted. Specific rate constants, k(E, J), calculated from the homogeneous linewidths, have been compared with results from SACM calculations, predictions from a statistical random matrix model, and ps time-domain measurements.
Highly ExcitedStates of NO2 2 * B ~ states J, N ', K' strongly perturbed predissociating A \ \ / J " , N " = 2, K" = 0 J " , N " = 0, K" = 0 x 2A, K l a = K ", bright state dark state LL X 2A, N::+ 1 N "'-1 4-1 N " + 1 N '' N " -1
