A shock tube study of the reactions of CH with CO 2 and O 2

The formation and consumption of CH radicals during shock‐induced pyrolysis of a few ppm ethane diluted in argon was measured by a ring‐dye laser spectrometer. Absorption‐over‐time profiles, measured at a resonance line in the Q ‐branch of the A 2 Δ − X 2 Π band of CH at λ = 431.1311 nm, were recorded and transformed into CH concentrations by known absorption coefficients. By adding some hundred ppm of CO 2 or O 2 to the initial mixtures, the CH concentration profiles were significantly perturbed. Both the perturbed and unperturbed CH concentration profiles have been compared with calculations based on a reaction kinetic model. A sensitivity analysis revealed that the perturbation process was dominated by direct reactions of CH with the added molecules. By fitting calculated to observed CH profiles the following rate coefficients were obtained\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH} + {\rm CO}_{\rm{2 }} \hbox to 22pt{\rightarrowfill}{\hskip-22pt ^{k_{{\rm{CO}}_2 }} \hskip0.265em}{\rm products} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH} + {\rm CO}_{\rm{2 }} \hbox to 18pt{\rightarrowfill}{\hskip-18pt ^{k_{{\rm{O}}_2 }} \hskip0.265em}{\rm products}$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm CO}_2 { }} = { 1}{.9 x 10}^{{14}} {\rm exp( - 7950 K/T) cm}^{3} {\rm mol}^{^{{ - 1}} } {\rm s}^{{ - 1}}$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm CO}_2 { }} { = 7}{.5 x 10}^{{13 }} {\rm cm}^{3} {\rm mol}^{{ - 1 }} {\rm s}^{{ - 1}}$$\end{document} The experiments were performed in the temperature range between 2500 K and 3500 K. © 1996 John Wiley & Sons, Inc.