Comparison of quasiclassical trajectory and classical S -matrix treatments of collinear collisions of F and D₂

The dynamics of collinear collisions of F with D₂(n ₁^a=0) have been studied using standard quasiclassical trajectory and classical S-matrix (semiclassical) techniques for collision energies ranging from 0.65 to 5.50 kcal mole^-1 in the center-of-mass system. The results are compared to previous quantum mechanical calculations on the same potential energy surface. At most only three transitions (NR 0→0, R 0→3, and R 0→4) are "classically allowed" at any energy studied. Of these, the only transition for which the "uniform semiclassical" and quasiclassical results are significantly different is R 0→4. The predicted energy dependence of this transition is discussed in terms of recent experimental determinations of the relative rates of R 0→4 and R 0→3. The "classically forbidden" R 0-2 transition is predicted (using the complex-valued trajectory method) to have a probability which exhibits distinct oscillations as a function of collision energy.