Experimental study on mid-infrared CO transition lines broadened by N2, He, and H2 at elevated temperatures

Abstract

Tunable diode laser absorption spectroscopy (TDLAS) has been established as a strong technique for high-fidelity measurements at elevated temperatures. However, the accuracy of the measured data using TDLAS depends on the accuracy of the spectroscopic parameters. In this paper, the N₂-, He-, and H₂-perturbed collisional broadening coefficients of the CO P(0, 21), P(1, 21), and P(0, 37) lines were measured at 1040–2980 K. Ar-diluted mixtures were applied to measure these spectroscopic parameters at elevated temperatures up to 3000 K. Validation experiments highlighted that the measured temperatures and CO concentrations agreed well with the known values under thermal equilibrium and nonequilibrium conditions. Comparisons of residuals in Voigt fitting highlighted that the N₂-perturbed Dicke narrowing effects are stronger than the He- and H₂-perturbed phenomena. The differences among species-perturbed high-temperature collisional broadening coefficients for the three transition lines were found to be closely related to the intermolecular forces and effective collision cross-sections.