Pressure-induced widths and shifts for the ν3 band of methane

Abstract
Widths and shifts of methane lines perturbed by nitrogen are calculated using a complex‐valued implementation of Robert–Bonamy (RB) theory. The static intermolecular potential is described as a sum of electrostatic forces and Lennard‐Jones (6‐12) atom–atom terms, using literature values for all physical parameters. Vibrational dependence of the isotropic potential is obtained from the polarizability of methane assuming a dispersion interaction. The repulsive part of the Lennard‐Jones accounts for the greatest part of widths, while dispersion interactions are largely responsible for shifts. Although the average error between calculated and observed linewidths (up to J=8) is less than 6%, their distribution suggests the influence of interactions not described in the present theory.

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