Calculation of interchange reaction rates by a `nearest resonance' method

Abstract

Thermal and suprathermal energy gas reaction rates for exothermic processes involving molecules or molecular ions are treated generally in terms of the adiabatic criterion. An absolute cross section function is derived in terms of a near-resonance energy defect which allows the determination of the dependence of reaction rate on temperature under conditions of complete or partial thermodynamic equilibrium. The reaction rates for seventeen exothermic processes are evaluated at 300°K and in many cases over a temperature range 150°K-4800°K: (i) under complete temperature equilibrium, (ii) with vibrational and rotational temperatures 300°K and (iii) at various vibrational temperatures of the diatomic partner but at a fixed translational and rotational temperature of T = 300°K. Special attention is given to aeronomically important reactions. It is apparent from these calculations that the exit channels of the triatomic quasi-molecule of collision are sufficiently well determined by the energy levels of the infinitely separated initial reactants to make the consideration of such levels useful in predicting reaction cross sections.