A wave packet method for treating nuclear dynamics on complex potentials

A general time-dependent description of the dissociative attachment of a triatomic molecule is presented. The approach presented works within the Feshbach projection operator formalism and gives an algorithm for solving the nuclear motion problem which reduces the computational effort required. The method uses a complex potential energy surface to characterize the formation and decay of resonances as modified by the coupling to the nuclear motion which are treated using multidimensional complex wave packets. A basis-independent wave packet method is developed and used to treat the propagation of a wave packet on a complex three-dimensional potential appropriate for resonance states of the water anion. A complete derivation of the system of linear equations used in the time iteration is presented. The method can be applied to resonant vibrational excitation, for which the electron impact vibrational excitation of water is considered.