In situ combustion measurements of CO2 by use of a distributed-feedback diode-laser sensor near 2.0 μm

High-resolution absorption measurements of CO2 were made in a heated static cell and in the combustion region above a flat-flame burner for the development of an in situ CO2 combustion diagnostic based on a distributed-feedback. diode laser operating near 2.0 mum. Calculated absorption spectra of high-temperature H2O and CO2 were used to find candidate transitions for CO2 detection, and the R(50) transition at 1.997 mum (the nu (1) + 2 nu (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 CO2 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. (C) 2001 Optical Society of America OCIS codes: 280.1740, 300.6260.