ELECTRON-PAIR WAVE-PACKETS

We present a computational scheme to propagate wave packets describing S states of two-electron systems. Body-fixed polar coordinates (r1, r 2, theta) are used to represent the time-dependent wave functions on a grid in three dimensions. We handle the Coulomb singularities by tran sformation of the wave function and a modified finite-difference formu la to evaluate the kinetic energy. We use a finite-difference split-op erator scheme for the time propagation and, as a first application, we compute the low-energy spectrum of helium and H-.