Reactive and nonreactive charge transfer by the FMS method: low energy H++D-2, and H+H-2(+) collisions

The full multiple spawning (FMS) methodology for solving the time dependent Schrodinger equation for multiple electronic states is extended to reactiv e collisions on several electronic states. The computational complexity rem ains unchanged, less than double that of a quasiclassical trajectory comput ation. It is shown how the spawning approach can describe the bifurcation o f the wave function into components exiting in different directions of spac e, as is the case when rearrangement of the atoms takes place. Low energy H + + D-2 and H + H-2 + collisions, which result in both reactive and nonreac tive charge transfer are used as an illustration. The FMS method is used to generate converged opacity functions and cross sections even at higher ene rgies when dissociation is energetically allowed. This suggests that also o n a single potential energy function the FMS method offers a viable route t o full dimensional reactive quantal scattering computations. For the H-3(+) system, a diatomics in molecules (DIM) potential energy function is used i n a diabatic basis where three electronic states are coupled. Comparison is made with the classical path approximation, the trajectory surface hopping method and stationary quantum mechanical scattering computations, which us ed the sudden approximation and the coupled states method. For the H+ + D-2 collision, our results are close to those already published. The computati ons for the H + H-2(+) collision, where the initial channel is an excited o ne, are distinctly different from the results of earlier, approximate, appr oaches.