Vibrational level dependence of lifetime of NO2 in the D̃2B2 state

The vibrational level dependence of the lifetime of NO2 D̃2B2 has been investigated by using LIF, hole-burning, and photofragment excitation methods. The predissociation rates for the vibrational levels estimated from the line profiles increase sharply with excitation energy even blow the second dissociation limit to form NO and O(1D). The occurrence of the dissociation pathway into NO and O(1D) via the D̃2B2 states is confirmed by the observation of the appearance thresholds to form various J″-levels of NO(2Π1/2, v″=0), which accord with the calculated dissociation limits. The dissociation mechanism is discussed based on the energy dependence of predissociation rates and O(1D) quantum yields.