Ultraviolet CO Chemiluminescence in CH(X2II) and CH(a4sigma-) Reactions with Atomic Oxygen at 298 K

摘要

Production of ultraviolet CO chemiluminescence has been observed for the first time in the gas-phase pulsed laser photolysis of a trace amount of CEBr3 vapor in an excess of O-atoms. O-atoms were produced by dissociation of O2 or N2O in 4 cw-microwave discharge cavity in 2.0 torr Heat 298 K. Temporal profiles of the excited state products that formed in the photo-produced precursor + O-atom (or O2) reaction were measured by recording their time- resolved chemiluminescence in discrete vibronic bands. The CO. 4th Positive transition (A1 II, v'=O -> x1sigma+, v'=2) near 165.7 nm, the CO Cameron band transition (a3H, v'=O % X1%+, v'%1) near 215.8 nm and the OH band transition (A2%+, v'=l % X211, v'=O) near 282.2 nm were monitored in this work to deduce the decay kinetics of the chemiluminescence in the presence of various' added substrates. From this the second-order rate coefficient values were determined for reactions of these substrates with the photo-produced precursors. Measured reactivity trends suggest that the prominent precursors responsible for the chemiluminescence are the methyfidyne radicals, CH(X2H) and CH(a4%-), whose production requires the absorption of at least 2 laser photons by the photolysis mixture. The 9-atom reactions with brominated precursors, which also form in the photolysis, are shown to play a minor role in the production of. the CO cherniluminescence. However, the CBr2 + 0-atom reaction was identified as a significant source for the ultraviolet Br2 chemilurninescence that was also observed in this work.