Aspects of nuclear dynamics in short-lived negative ion states

The nonlocal potential theory of nuclear motion in resonance states and weakly bound states of negative ions is reviewed. The ab initio calculation of the electronic width and level-shift functions, which determine the nonlocal part of the potential for the nuclear motion, is briefly discussed. Methods to solve the nuclear dynamical problem taking full account of the nonlocality of the potential are described. Illustrative calculations are presented for vibrational excitation of N₂ via the 2.3-eV shape resonance, as well as for a realistic model of dissociative attachment. It is shown that the widely used local complex potential approximation (boomerang model) is of excellent accuracy for vibrational excitation of N₂. In other situations the local approximation is less reliable; this is demonstrated for shape resonances with repulsive potential energy curves such as in the halogen anions.