Theoretical calculations for line-broadening and pressure-shifting in the fundamental and first two overtone bands of CO–H2

The line broadening and shift coefficients for CO–H2 in the fundamental and first two overtone bands are modeled using semi-classical calculations based on the Robert–Bonamy formalism and two isotropic and anisotropic intermolecular potentials. These potentials involve electrostatic contributions and (a) the atom–atom Lennard-Jones model, or (b) the Tipping–Herman model with adjustable parameters in order to fit the broadening coefficients. For the line shifts, which appear to arise only from vibrational dephasing effects, different values for the relative dependence of the attractive and repulsive parts of the isotropic potential are used. The calculated broadening and shift parameters are then compared with experimental results available in the literature. This comparison shows a reasonable agreement of the broadening parameters and a less satisfactory agreement of the line shifts for which the experimental data are on the whole rather inaccurate. q 2005 Elsevier B.V. All rights reserved.