Direct measurement of 1CH2 in flames by cavity ringdown laser absorption spectroscopy

Singlet methylene is an important combustion intermediate, but has remained difficult to measure in flames. Cavity ringdown laser absorption spectroscopy (CRLAS) allows the sensitive and selective detection of 1CH2 with good spatial resolution. Singlet methylene has been detected by CRLAS in a series of rich, low-pressure methane flames with stoichiometries of 1.0, 1.2, 1.4 and 1.6. The measured relative concentration profiles are compared with laminar flame models utilizing detailed chemical reaction mechanisms. The data show good agreement with models at stoichiometries of 1.0 and 1.2, but increasingly poor agreement at richer stoichiometries.