Classical trajectory studies of long-lived collision complexes. I. Reaction of K atoms with NaCl molecules

Abstract

We have studied the reaction K+NaCl→KCl+Na using classical trajectory techniques on an analytic potential energy surface fit to the ground-state semiempirical pseudopotential surface of Roach and Child. A total of 8000 trajectories were calculated in order to study product angular distributions, energy partitioning and complex lifetimes as a function of collision energy. The ``snarled'' trajectories, the shapes of the center-of-mass angular distributions, and the disposal of energy all provide evidence that reaction proceeds via the formation and subsequent decomposition of long-lived complexes. The calculated laboratory angular distribution of KCl product and the magnitude of the reaction cross section are in reasonably good agreement with experimental results from molecular beam studies by Miller, Safron, and Herschbach. However, the predicted ratio of reactive-to-nonreactive complex decompositions is too large and, since the surface used has too weak a long-range K–Na attraction, these results support the earlier suggestion that many nonreactive decompositions result from linear complexes formed with the wrong orientation. Comparison with other trajectory calculations reemphasize the importance of the height and shape of the entrance and exit-channel barriers in determining both complex formation and reaction dynamics.