RESONANCES AND FLUCTUATIONS IN THE UNIMOLECULAR REACTION OF NO2

Fluctuations and oscillations in the unimolecular reaction of NO2, and their manifestations in photofragment yield (PHOFRY) spectra, NO rota tional state distributions and decomposition rates are examined. Compa risons between experimental and simulated PHOFRY spectra show that ext raction of rates from linewidths in state-selected spectra is unjustif ied in the regime of overlapping resonances. Measurements of the align ment parameter of the NO product in the excess energy range E-E = 200- 500 cm(-1) evidence the existence of fluctuations in the decay rate. C hanges in the patterns of fluctuations and oscillations in the NO rota tional state distributions reveal the progressive tightening of the tr ansition state (TS) as the excess energy increases and the importance of exit-channel interactions beyond the TS. Distributions well fit on the average by phase-space calculations can be obtained even when the transition state is tight.