High-temperature line strength and line shape parameters measurements of Ar- and N2-perturbed CO2 lines near 4.18 µm in a shock tube

Abstract

Line strengths and line shape parameters of Ar- and N₂-perturbed CO₂ R-branch transitions (82 $\le J^{″}\le$ 90) in the ${\nu }_3$ fundamental band were measured in a shock tube from 730 K to 2500 K and pressure below 1.13 atm using laser absorption spectroscopy (LAS). The retrieved absorption curves were fitted with the Voigt and the quadratic speed-dependent Voigt (qSDV) profiles to obtain the line strengths, broadening, and shift coefficients. Line strengths were compared to values in HITEMP, HITRAN2020, and Ames2021 databases, and the HITEMP shows the best agreement with the measured results. Ar- and N₂-broadening and shift coefficients were regressed into the power law and the double power law form to study the temperature dependence of the targeted lines. The speed-dependence parameter $a_w$ was temperature-dependent. The J-dependence of the derived broadening and shift coefficients was discussed. The results of this work will aid the development of the absorption model in the far-wing region and the design of CO₂ LAS sensors for high-temperature measurement.