High‐temperature reaction of C 2 with NO including product channel measurements

The reaction of C 2 radicals with NO was studied behind reflected shock waves in the temperature range 3150 K≤ T ≤3950 K. The shock‐induced pyrolysis of acetylene, highly diluted in argon, was used as a well defined source for C 2 radicals, which were detected by ring‐dye‐laser absorption spectroscopy (RDLAS) at 516.646 nm. The perturbation of the C 2 by the addition of NO to the initial mixtures results in a fast removal of the C 2 radicals, which is mainly caused by the reaction: (R5)$$ C_{2} + NO {\buildrel k_{5} \over \longrightarrow}\hbox{products}$$ for which the overall rate coefficient$$k_{5}=\rm 7.5\times 10^{13}\times\hbox{exp}(-4350/\it T)\rm cm^{3}mol^{-1}s^{-1}$$ was obtained. The product channels of this reaction were studied by additional measurements of O‐atoms, N‐atoms, and CN radicals. O and N were detected using atomic resonance absorption spectroscopy (ARAS) and the CN radicals were followed by their emission using a spectrograph and an intensified CCD‐camera. The reactions leading to the product channels C 2 N+O (R5a) and to C 2 O+N (R5b) were identified as the main channels with a branching ratio of k 5a / k 5 =70% and k 5b / k 5 =30%, while the channel leading to CN+CO (R5c) was found to be neglectable. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 11–21, 1999