Temperature dependence of termolecular association of diatomic ions with diatomic molecules

The dependence of the rate coefficient k for termolecular association between diatomic ions A+ and diatomic molecules B on the temperature T of the ambient gas M is considered. There is experimental evidence that k decreases rapidly as T is increased if the association energy is small. A proposal that this behavior may be explained by the introduction of a super-complex AB+⋅M is rejected. It is shown that required T variation could ensue if the reactants in the energized AB+* complex repel one another at some relative orientations.