Application of continuous-wave cavity ring-down spectroscopy to laminar flames

In this paper we describe the application of diode laser continuous-wave cavity ring-down spectroscopy (cw-CRDS) to in-situ flame diagnostics. Spectra of the P17e acetylene feature at 1535.4 nm were recorded in a premixed laminar ethylene/air flame. The overall absorption of the feature was measured to be ≈ 1.5×10⁻⁴ cm⁻¹ a short distance above the reaction zone for a flame fuel equivalence ratio of 1.66, and the minimum detection limit (3σ) of the system was calculated to be1.2×10⁻⁵ cm⁻¹. This demonstrates the potential of the technique for the measurement of weakly absorbing species in flames. Finally, we discuss the advantages and limitations of the cw-CRDS technique for flame measurements.