Differential cross sections of F plus HD -> DF plus H reaction at collision energies from 3.03 MeV to 17.97 MeV

The prototypical reaction of F+HD -> DF+H was investigated at collision energies from 3.3 meV to 17.97 meV using a crossed molecular beam apparatus with multichannel Rydberg tagging time-of-flight detection. Significant contributions from both the Born-Oppenheimer (BO) forbidden reaction F*(P-2(1/2))+HD -> DF+H and the BO-allowed reaction F(P-2(3/2))+HD -> DF+H were observed. In the backward scattering direction, the contribution from the BO-forbidden reaction F*(P-2(1/2))+HD was found to be considerably greater than the BO-allowed reaction F(P-2(3/2))+HD, indicating the non-adiabatic effects play an important role in the dynamics of the title reaction at low collision energies. Collision-energy dependence of differential cross sections (DCSs) in the backward scattering direction was found to be monotonously decreased as the collision energy decreases, which does not support the existence of resonance states in this energy range. DCSs of both BO-allowed and BO-forbidden reactions were measured at seven collision energies from 3.03 meV to 17.97 meV. It is quite unexpected that the angular distribution gradually shifts from backward to sideway as the collision energy decreases from 17.97 meV to 3.03 meV, suggesting some unknown mechanisms may exist at low collision energies.