Understanding the seemingly simple dissociation of NO2 : Statistical classical trajectory studies and comparison with experiments

Classical trajectory calculations for the capture process O + NO → NO 2 on potential energy surfaces of NO] in the electronic X- and C-states, which are based on ab initio calculations, are reported. Capture probabilities are determined as a junction of the total energy E and the total angular momentum (quantum number J) of the system, and are related with numbers of open channels W(E,J) of the dissociation/association process. The combination with rovibrational densities of states p(E,J) leads to statistical rate constants k(E,J) for dissociation of NO 2 . Anharmonic rovibrational densities of states are estimated for the electronic X-, A-, B-, and C-states of NO 2 . The role of these states in experimentally observed dissociation studies is discussed. Agreement with time- and state-resolved measurements of k(E,J) is found over wide ranges of E and J, although some discrepancies are noticed at small J and at energies close to the dissociation threshold. Apart from this range, there does not appear to be significant experimental evidence for incomplete K-mixing during the dissociation process. There is also no evidence that steps, such as observed in some experimental k(E,J) curves, correspond to transition state levels.