CO₂-broadening coefficients in the ν3 fundamental band of methane

In this paper, CO ₂ -broadening coefficients of 11 lines in the ν ₃ band of CH ₄ , located between 2906 and 2959 cm ⁻¹ , were measured at room temperature using an improved tunable diode-laser spectrometer. Each line was recorded for 4 different pressures, ranging from 20.15 to 60.20 mbar. The experimental determination of the CO ₂ -broadening coefficients was performed by fitting a theoretical profile on the experimental line shape for each line recorded at each pressure. The Voigt, Rautian-Sobel'man and Galatry models were therefore used. The ratio between the present CO ₂ -broadened results and the data available in the literature for air-broadening is investigated and compared to the ratio between N ₂ - and air-broadening. The γ _{CO 2} /γ _air presents significant differences with the ratio γ _{N 2} /γ _air as well as a large scattering. This shows the need to make dedicated studies, both experimentally and theoretically, for CO ₂ -broadening coefficients.