Spatially homogeneous relaxation of CO molecules with resonant V E transitions

Abstract

In this paper we study vibrational relaxation of CO molecules with excited electronic states. We consider three electronic terms and account for V V exchanges of vibrational energy within each electronic term, V T transitions of vibrational energy into translational and V E exchange of vibrational energy between electronic terms. The initial vibrational state of the gas is strongly non-equilibrium. The effect of V E exchange on the vibrational relaxation of CO molecules is evaluated for different kinds of initial vibrational distributions, in particular, the Treanor and Gordiets ones generalized for gases with electronically excited states. The set of equations of state-to-state vibrational kinetics coupled to the gas-dynamic equations is solved numerically in the zero-order approximation of the Chapman-Enskog method for the case of spatially homogeneous relaxation. The following results were obtained: neglecting V E exchanges leads to an incorrect assessment of the numerical density for each electronic level, however, the error is small for the ground electronic state. It is shown that V E exchanges qualitatively affect the time dependence of the vibrational temperature. Refs 17. Figs 5.