Helium and Argon Line Broadening in the nu2 Band of CH4

International audienceThe spectra of the gaseous mixtures CH4-He and CH4-Ar were obtained in the spectral region 1400-1750 cm-1 with a resolution up to 0.003 cm-1. Helium and argon pressure broadenings for the vibration-rotation lines of the nu2 band of CH4 have been estimated at room temperature for some lines in the P, Q, and R branches. These values were also calculated using the theoretical approach developed by Robert and Bonamy, extended to the case of tetrahedral molecules. The helium data have been found to be in a satisfactory agreement whereas a divergence of calculated and measured broadening coefficients has been evidenced in the case of argon. Simulations of the nu2 band shapes of methane perturbed by helium have also been performed