Intracavity laser absorption spectroscopy of flames: concentration measurements of intermediate species

Intracavity laser absorption spectroscopy was used to study concentration profiles of several radicals in flames. Very high sensitivity of ICLAS enables quantitative measurements of absolute concentrations of atoms and radicals in flames. MOst of the experiments were done with a flat flame burner placed inside the cavity of a broad band dye laser. The spectra of HCO radicals and CH2 radical, in the singlet electronic state were measured with a high signal-to-noise ratio at different position above the burner.In this work we report the measurement of the concentration profiles of HCO and CH2 radical sin methane/air flame. The spectra of these two radicals can be measured simultaneously which is advantageous in combustion diagnostics. Cavity ring-down laser spectroscopy was used to measure the OH concentration profiles of the HCO and OH radicals are in reasonable agreement with computer simulation results. However, a rough estimation of the CH2 absolute concentration indicates a much higher concentration than that which can be predicted based on the model calculation.