Formation of N2(A3Σu+) and N(2D, 2P) by Photodissociation of HN3 and N2O and Their Reactions with NO and N2O

The formation of NO (A 2Σ+) and NO (B 2II) in the photolysis of N2O at 1236 and 1470 Å was investigated by observing the fluorescence of the γ and β bands. The β-band fluorescence is obtained when pure N2O is photolyzed at 1236 and 1470 Å in a flow system. The β bands are observed with vibrational excitation up to v′=3. The β bands disappear with the addition of small amounts of NO, whereas the emission of rotationally hot γ bands is obtained. The γ bands are observed with vibrational excitation up to v′=2. According to the energetics, NO (A 2Σ+) and NO (B 2II) are formed at 1470 Å as well as at 1236 Å not by direct photodissociation of N2O but by secondary reactions. No fluorescence is obtained when N2O or N2O/NO mixtures are irradiated at wavelengths ≧1600 Å, i.e., within the long-wavelength absorption band of N2O. The roles of N2 (A 3Σu+), N (2D), N (2P) are evaluated and discussed. The emission of γ bands is also obtained in the photolysis of HN3/NO mixtures at 1470 and 1236 Å. This observation is explained by the photodissociationHN3→N2(A Σu+)+NH(X 3Σ−)followed by the reaction between N2 (A 3Σu+) and NO, yielding NO (A 2Σ+). The other possibility, that O atoms which are formed by photodissociation of NO react with HN3 to form excited NO—as in the O/N2H4 atomic flame—is excluded.