CO2-broadening coefficients in the ν3 fundamental band of methane

Abstract

In this paper, CO2-broadening coefficients of 11 lines in the ν3 band of CH4, 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 CO2-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 CO2-broadened results and the data available in the literature for air-broadening is investigated and compared to the ratio between N2- and air-broadening. The γCO2/γair presents significant differences with the ratio γN2/γair as well as a large scattering. This shows the need to make dedicated studies, both experimentally and theoretically, for CO2-broadening coefficients.