Quantum mechanical angular distributions for the F+HD reaction

Quantum-mechanical integral and differential cross-sections have been calcu lated for the title reaction at the two collision energies (E-coll - 1.35 a nd 1.98 kcal mol(-1)) studied in the 1985 molecular beam experiment of Lee and co-workers, using the new ab initio potential-energy surface of Stark a nd Werner. The DF + H product channel is found to behave essentially classi cally: the present quantum-mechanical angular distributions for this channe l are in good agreement with both the earlier quasi-classical trajectory re sults of Aoiz and co-workers on the same potential-energy surface and the r esults of the molecular beam experiment. However, the HF + D product channe l in which the light H atom is transferred between two heavier atoms is inh erently more quantum-mechanical: our computed angular distributions for thi s channel differ significantly from the quasiclassical trajectory results a nd agree better with the results of the experiment (especially at the highe r of the two experimental collision energies). The main quantum-mechanical effect that is identified in the calculations is a reactive scattering reso nance that gives rise to a pronounced forward-scattering peak in the calcul ated F + HD(v = 0, j = 0) --> HF(v' = 3) + D differential cross-section. Th e influence of this resonance on the reaction dynamics is discussed in some detail, together with the implications of our results at the lower of the two collision energies for an improvement to the Stark-Werner potential-ene rgy surface.