Speed-dependent line-shape models analysis from molecular dynamics simulations: The collision regime

A spectral line-shape model accounting for the speed dependence of the relaxation parameters has been proposed for the collision regime [D. Robert et al., Phys. Rev. A 47, R 771 (1993)]. In this model, the speed class exchanges are governed by a memory parameter playing a crucial role. It has been exhaustively used to accurately describe the observed inhomogeneous features of H₂ vibration line profiles in various mixtures with respect to concentration and temperature. Molecular dynamics calculations of the characteristic memory parameter are performed in order to test this model from first principles. The resulting data are in remarkable agreement with those deduced from experiments through the model.