Cavity ringdown laser absorption spectroscopy detection of formyl (HCO) radical in a low pressure flame

The formyl radical has been detected via the Ã-X̃ system in a low pressure CH4/N2/O2 flame using cavity ringdown laser absorption spectroscopy. The direct absorption data obtained in these initial studies allows determination of the absolute HCO concentration in the flame of ca. 2.1(±0.9) × 1013 mol cm−3, which is in excellent agreement with flame chemistry simulations. The extrapolated detection limit at 300 K of ≈ 1.4(±0.6) × 1011 mol cm−3 is comparable to that of other methods, including intracavity laser absorption spectroscopy.