CH(A2Δ) Formation in Hydrocarbon Combustion: The Temperature Dependence of the Rate Constant of the Reaction C2H + O2 → CH(A2Δ) + CO2

The temperature dependence of the rate constant of the chemiluminescence reaction C2H + O2 → CH(A) + CO2, k1e, has been experimentally determined over the temperature range 316−837 K using pulsed laser photolysis techniques. The rate constant was found to have a pronounced positive temperature dependence given by k1e(T) = AT4.4 exp(1150 ± 150/T), where A = 1 × 10-27 cm3 s-1. The preexponential factor for k1e, A, which is known only to within an order of magnitude, is based on a revised expression for the rate constant for the C2H + O(3P) → CH(A) + CO reaction, k2b, of (1.0 ± 0.5) × 10-11 exp(−230 K/T) cm3 s-1 [Devriendt, K.; Van Look, H.; Ceursters, B.; Peeters, J. Chem. Phys. Lett. 1996, 261, 450] and a k2b/k1e determination of this work of 1200 ± 500 at 295 K. Using the temperature dependence of the rate constant k1e(T)/k1e(300 K), which is much more accurately and precisely determined than is A, we predict an increase in k1e of a factor 60 ± 16 between 300 and 1500 K. The ratio of rate constants k2b/k1...