Seven Mechanisms in the Photolysis of No2 Between 3100 and 3700 Å

Nitrogen dioxide has been photolyzed by various investigators under seven different limiting conditions, all at wavelengths between 3100 and 3700 Å. The results are reviewed and discussed in terms of two general mechanisms, both of which quantitatively relate the experimental data. The mechanisms differ in that one postulates that atomic oxygen attacks NO2 in two ways, yielding NO and O2 in one case and excited NO3 in the other. The excited NO3 can decompose to form atomic oxygen and NO2; it can be deactivated, or it can react with NO2. The second mechanism postulates a single mode of attack on NO2 by atomic oxygen, again yielding excited NO3. The NO3 can decompose to form NO and O2; it can be deactivated, or it can react with NO2. Of the two mechanisms the first seems more consistent with the thermal reactions of NO2 and NO3. It is believed that both the linear and the triangular NO3 play important roles in the photolysis.