Hydrogen-broadening coefficients in the ν5 band of CH3F at room and low temperatures

Using a tunable diode-laser spectrometer, H2-broadening coefficients have been measured for 46 lines of CH3F at room temperature (297.2 K), 5 lines at 223.2 K and 22 lines at 183.2 K in the ν5 fundamental band near 6.6 μm. These lines were individually fitted with Voigt, Rautian, and Galatry profiles in order to determine their collisional widths. The resulting broadening coefficients are compared with theoretical values derived from a semiclassical theory involving two intermolecular potentials. In addition to electrostatic contributions, the first potential involves induction and dispersion contributions and the second potential the atom-atom Lennard-Jones model. Comparing broadening coefficients at room and low temperatures, the temperature dependence of these broadenings has been determined both experimentally and theoretically.