H+ +H, HE, AND H-2 SCATTERING USING A NEW TIME-DEPENDENT METHOD FOR ELECTRON-NUCLEAR DYNAMICS

In this paper we apply the recently proposed and implemented electron nuclear dynamics (END) theory [J. Chem. Phys. 96, 6820 (1992)] to the study of prototypical ion-atom and ion-molecule collisions. The END theory obtains the equations of motion from the time-dependent variational principle (TDVP) employing a group theoretical coherent state (CS) parametrization of the wave function. The approach leads to a fully dynamical treatment of electrons and nuclei without invoking potential energy surfaces. The present implementation of the END theory constitutes the simplest ab initio model with the electrons described by a single determinantal wave function and the nuclei treated classically (or equivalently, with frozen Gaussian wave packets in the limit of a narrow widths). The method is applied to the H+ + H, He, and H-2 collision processes in the energy range of 200-5000 eV. Results for the elastic and charge transfer differential cross sections, the differential probabilities, and the rainbow angles are presented and compared with experimental data. Also, the dynamical trajectories, deflection functions, and differential vibrational excitation for the H-2 target are calculated and discussed. Effects of initial state molecular orientations, in the case of the H-2 target, are considered. In general, the results provided by this model implementation of the END theory are in good agreement with experimental data.