Vibrational relaxation of diatomic hydrides in inert gases. Rate constant calculations

Abstract

Systematic calculations of thermal rate constants of vibrational relaxation of diatomic hydrides (HX) in inert gases (A) have been carried out for all available potential of such pairs. The method of calculation is based on a static approximation with respect to relative motion and includes a numerical calculation of Fourier harmonics of the perturbation during rotational motion of the molecule in the potential of the pair AHX. For all systems AHX, A = He, Ne, Ar, Xe, X = HCl, HF, OH, DCl, etc. the theoretical rate constants obtained with the power-type potentials (by Lennard-Jones, or Howard and Hutson) are significantly larger than experimental data. For available exponential-type potentials of ArHCl or the ab initio potentials of Ar, He + HF there is reasonable agreement between calculated and experimental data. The mechanism of VR relaxation is specified: the large contribution of trajectories with quasi-free molecule rotation passing through the linear configuration AHX has been established. Estimates of the rate constants as a function of initial rotational energy permit us to discuss the role of VR processes in recently observed laser effects on the rotational transition of hydrides.