In situ combustion measurements of CO_2 by use of a distributed-feedback diode-laser sensor near 20 µm

High-resolution absorption measurements of CO(2) were made in a heated static cell and in the combustion region above a flat-flame burner for the development of an in situ CO(2) combustion diagnostic based on a distributed-feedback diode laser operating near 2.0 mum. Calculated absorption spectra of high-temperature H(2)O and CO(2) were used to find candidate transitions for CO(2) detection, and the R(50) transition at 1.997 mum (the nu(1) + 2nu(2) + nu(3) band) was selected on the basis of its line strength and its isolation from interfering high-temperature water absorption. Measurements of spectroscopic parameters such as the line strength, the self-broadening coefficient, and the line position were made for the R(50) transition, and an improved value for the line strength is reported. The combustion-product populations of CO(2) in the combustion region above a flat-flame burner were determined in situ to verify the measured spectroscopic parameters and to demonstrate the feasibility of the diode-laser sensor.