| Abstract: | An ArF excimer laser was used to perturb radical concentrations and a tunable dye laser was used to follow the rise and subsequent decay of OH and CH in rich (? = 1.6–1.8) atmospheric pressure methane flames. The excimer beam is only slightly focussed to minimize temperature excursions and the influence of diffusion and convection on the decay rates. The observed OH decay is consistent with that predicted using a detailed kinetic mechanism. The observed CH decay is much faster than predicted. The effects of equivalence ratio and height above burner suggests that a major CH decay channel involving an intermediate with higher concentration in rich flames is not properly treated in the mechanism. |
