STATE-RESOLVED DYNAMICS IN HIGHLY EXCITED-STATES OF NO2 - COLLISIONALRELAXATION AND UNIMOLECULAR DISSOCIATION

Recent state-resolved investigations of unimolecular dissociation and collisional relaxation of NO2 at chemically significant internal energ ies are outlined. Two powerful double-resonance techniques are describ ed which permit the investigation of these processes on a quantum-stat e-resolved level of detail. A sequential optical double-resonance tech nique with sensitive laser-induced fluorescence detection has been emp loyed for assignments of the molecular eigenstates of NO2 in the energ y range at 17 700 cm(-1). Subsequently, we were able to measure state- to-state rotational and vibrational energy transfer in NO2-NO2 self-co llisions using a time-resolved double-resonance technique. From these data, direct information about propensity rules and intermolecular int eractions for rotational and vibrational energy transfer in NO2 self-c ollisions at high vibrational excitation could be obtained. In additio n, we have used a folded high-resolution V-type double-resonance techn ique in a free jet to access and to assign rovibronic states of NO2 ab ove and below the dissociation threshold, E-0. From the double-resonan ce spectra, linewidths at around 25 130 cm(-1) as a function of intern al energy, E, and total angular momentum, J, could be extracted. Speci fic rate constants, k(E, J), calculated from the homogeneous linewidth s, have been compared with results from SACM calculations, predictions from a statistical random matrix model, and ps time-domain measuremen ts.