On the Effect of Initial Rotation on Reactivity. A Multi-Configuration Time-Dependent Hartree (MCTDH) Wave Packet Propagation Study on the H + D2 and D + H2 Reactive Scattering Systems

Cumulative initial-state-selected reaction cross sections of the H + D 2 and D + H 2 systems are analyzed for collision energies up to 1.3 eV. Initial states of the diatom with rotational quantum numbers j 0 = 0−4 and vibrational quantum number v 0 = 0 are considered. The Liu−Siegbahn−Truhlar−Horowitz (LSTH) potential energy surface is taken as interaction potential. The geometric phase is ignored but no further (nonnumerical) approximations are made. The cross sections are computed by propagating wave packets employing the multiconfiguration time-dependent Hartree scheme. The reactive flux, which determines the integral cross section, is evaluated through the interaction of the wave packet with a complex absorbing potential. The initial-state-selected integral cross sections, σ j 0 ( E ), in particular those for j 0 = 0, show weak oscillations, which we attribute to transition state resonances associated with excitations of the bending motion. Some of the present results are discussed in comparison with results obtained by using the coupled states approximation.