Quantum effects in Ar+HF rotationally inelastic scattering: A semiclassical interpretation

Invoking a semiclassical approach to state-to-state rotationally inelastic scattering, this study seeks to determine the origin of several novel features observed in earlier quantum mechanical calculations [Rawluk et al., Chem. Phys. Lett. 202, 291 (1993)]. These features were absent from comparable classical trajectory calculations. The semiclassical (classical path) method used here treats the relative motion of Ar and HF classically, while the HF rotation is treated quantum mechanically by expansion in a rigid rotor basis set. This semiclassical approach reproduces the exact quantum results very well. The time dependence of the classical path allows a detailed study of the role played by the potential energy surface governing the dynamics. In particular, the behavior of the expansion coefficients 〈Y_jm|Ψ(t)〉 in the complex plane is very revealing. From this analysis, it is clear that the quantum effects stem from a balance between the attractive and repulsive parts of the potential.