Measurements of the absolute concentrations of HCO and (CH2)-C-1 in a premixed atmospheric flat flame by cavity ringdown spectroscopy

Singlet methylene (1CH2) and the formyl radical (HCO) have been studied in a premixed flat flame of CH4 and air by cavity ring-down spectroscopy at 1 atm. The absorption lines lie in the same spectral region for both species. The 1CH2 radicals were probed via the 1B1 (0,13,0) ¿ã1A1 (0,0,0) band at 622 nm and the HCO radicals via the Ã2A' (0,9,0) ¿ 2A¿ (0,0,0) band at 615 nm. Absolute concentrations of 1CH2 and HCO have been obtained at various heights above the burner and compared to numerical simulations using both the GRI-Mech 2.11 and 3.0 mechanisms, showing relatively good agreement