Filtering Reaction Dynamics Using Nearside-Farside Theory and Local Angular Momentum Theory: Application to the Angular Scattering of the H + D2(νi=0, ji=0) → HD(νf=3, jf=0) + D Reaction in the Energy and Time Domains

We investigate methods for filtering reaction mechanisms in the angular scattering of the state-to-state reaction, H + D-2(nu(i) = 0, j(i) = 0, m(i) = 0) -> HD(nu(f) = 3, j(f), = 0, m(f) = 0) + D, where nu(i), j(i), and m(i) and nu(f), j(f), and m(f) are initial and final vibrational, rotational, and helicity quantum numbers, respectively. The input to our filtrations is a new set of accurate quantum scattering matrix elements for total energies in the range 1.52-2.50 eV (in steps of 0.01 eV) and for total angular momentum quantum numbers in the range, 0-40, in steps of unity. We filter reaction mechanisms in both the energy domain and the time domain. The time-domain calculations employ the plane wave packet formulation of time-dependent scattering. The theoretical tools used are nearside-farside (NF) analysis of partial wave series for scattering amplitudes, together with NF local angular momentum (LAM) theory. An energy-domain LAM analysis reveals the existence of an important dynamical feature in the N scattering, a trench which bisects the (energy, angle) plane. We use the location of this trench to approximately filter two reaction mechanisms. Transformation to the time domain demonstrates that the two reaction mechanisms correspond to direct and delayed (by about 25 fs) scattering. Further analysis, including filtration in the time domain, shows that the pronounced LAM trench arises from the interference of the energy-domain analogues of the time-direct and time-delayed scattering. Our theory and results provide the first successful demonstration of reaction mechanism filtering carried out directly in the (energy, angle) domain. The calculations and results in this paper extend and complement earlier research reported by Monks, Connor, and Althorpe (Monks, P. D. D.; Connor, J. N. L.; Althorpe, S. C. J. Phys. Chem. A 2006, 110, 74 1; J. Phys. Chem. A 2007, 111, 10302).