Temperature dependence of rotationally inelastic rate constants fitting laws

Abstract

The recently developed quasiclassical ECS-E fitting law has been employed to study the temperature dependence of rotational energy relaxation rates. By comparing the rotational energy relaxation cross-sections given by the phenomenological and microscopic approaches, we have derived the relationship between the intermolecular potential parameters and three independent parameters of the model, thus deriving the temperature-dependent form of the quasiclassical ECS-E law. The ability of our model to predict the temperature dependence of the energy relaxation cross-section and the widths of the Raman Q-branch isolated lines has been tested with nitrogen as an example. The method for the determination of anisotropy parameters of the potential (in the form of a non-spherical Morse potential) has been suggested, on the condition that numerical values of the model parameters are determined through an inversion-fitting procedure from the Q(j)-line-broadening coefficients. The primary advantage of our approach is the possibility of calculating rotational relaxation rates from the given form of the interaction potential. This possibility is illustrated by the calculation of the argon-broadening coefficients for nitrogen Q-branch lines and the rotational energy relaxation cross-section for this system.