SEMICLASSICAL CALCULATIONS ON THE ENERGY-DEPENDENCE OF THE STERIC EFFECT FOR THE REACTION CA(D-1)-]CAF+CH3(CH3F(JKM=111))

In a previous article [A. J. H. M, Meijer, G. C. Groenenboom, and A. v an der Avoird, J. Chem. Phys. 101, 7603 (1994)] we investigated the en ergy dependence of the steric effect of the reaction Ca (D-1)+CH3F (jk m = 111)-->CaF (A (II)-I-2)+CH3 using a quasiclassical trajectory meth od. It was found that we could not reproduce the experimental results for this reaction [M. H. M. Janssen, D. H. Parker, and S. Stolte, J. P hys. Chem. 95, 8142 (1991)]. In this article, we reinvestigate this re action using a semiclassical method, in which the rotation of the mole cule and the electronic states of the interacting atom and molecule ar e Created quantum mechanically. For the chemical reaction we use a mod el which correlates the projection of the electronic orbital angular m omentum of the Ca atom on the intermolecular axis with the projection of the electronic orbital angular momentum of the CaF product on the d iatomic axis [M. Menzinger, Polon. Phys. Acta A 73, 85 (1988)]. This m odel is applied to examine the CaF (A (II)-I-2, B (2) Sigma(+), A'(2) Delta) exit channels separately. We conclude that we can reproduce the experimental;results for the steric effect using this model. The impr ovement with respect to the classical trajectory results is shown to b e due primarily to the extended reaction model rather than to the semi classical description of the dynamics. We find trapping and reorientat ion in the semiclassical calculations, as in the previous classical tr ajectory results, but also non-adiabatic effects are present. The latt er do not affect the reactive cross sections very much. (C) 1996 Ameri can Institute of Physics.