Pressure broadening study at low temperature: application to methane

We studied the R(0) line profile in the CH 4 ν 4 band from room temperature to 188 K with N 2 as a perturber, to 100 K with O 2 as perturber, and from room temperature to 15 K using He as a perturber. The N 2 and O 2 measurements were performed over a total pressure range of 15–110 mbar, and for the He measurements the maximum sample pressure at 15 K was 1.10 mbar. Broadening parameters were determined, taking into account the confinement narrowing (Dicke effect), and narrowing parameters, deduced from the soft or hard collision model, are compared with the dynamic friction coefficient calculated values. We also obtained preliminary values for the temperature dependence of the N 2, O 2 and He line broadening parameters for this transition.