A kinematic, classical mechanical theory of reactive collisions

A classical mechanical theory has been formulated for reactions of the form A+BC → AB+C. The essential features of the model are a classical Franck–Condon transition from reactants to products, and the use of kinematics to describe relative motion of the reactants and the products. In the present work, the theory has been applied to reactant–product angular momentum coupling. The general limiting cases of light- and heavy-atom transfer reactions are discussed. Comparison with the quantum theory of Schulten and Gordon [J. Chem. Phys. 64, 2918 (1976)] shows excellent agreement between the classical and the quantum theories, particularly for the location and magnitude of the peak in the product angular momentum distributions. The classical theory has the advantage that the contributions of different reactant orientations can be obtained separately. Comparisons are made between product angular momentum distributions obtained from the present model and from quasiclassical trajectory calculations. The agreement between the two sets of results can be excellent, e.g., for F+D2 → DF+D, clearly showing that for some reactions kinematic coupling of the reactant and product states can dominate the coupling between states due to the interaction potential.