PRODUCT YIELDS AND MECHANISM OF THE EXCIMER LASER PHOTOLYSIS OF AZOMETHANE AT 193 NM

The photodecomposition of azomethane by single pulse excimer laser photolysis at 193 nm has been studied by using end product analysis and Lyman α resonance fluoresence. The major product (≳90%) was ethane, as expected, but methane, ethene, ethyne, and propane were also formed in small quantities. The methane and ethene yields were observed to increase with increasing pulse energy, while the propane yield remained constant. Lyman α resonance fluorescence shows that H atoms are produced directly by photolysis and that, at high pulse energies, they are also formed by a secondary reaction. Two minor H-producing photolysis channels are indicated, the first producing H + CH2N2CH3 and the second involving secondary photolysis of vibrationally excited CH3 radicals and producing H + CH2; the fractional product yields from the second channel increase linearly with pulse energy. A rate constant of (3.4 ± 0.2) × 10-12 cm3 molecule-1 s-1 is obtained for the reaction of H atoms with azomethane at 300 K. © 1987 American Chemical Society