The evolution of entropy along the reaction path in an atom-diatom collision

The distribution of vibrational states at any point along the reaction path is obtained, in the classical path limit, for a model reactive collision problem. For reactants in the ground vibrational state the distribution is of a Poisson-type throughout the reaction, and hence the entropy can be analytically computed. It is shown that there may be more extensive vibrational population inversion at an intermediate point as compared to the final products.