Diatomics-in-molecules study of the ground and excited states of H-3(-)

A systematic diatomic-in-molecules procedure is applied to the H-3(-) system to calculate the potential energy surfaces of the ground and low-lying excited states over the full range of geometric configurations. The approach provides the correct behavior of the calculated potentials. A conical intersection of the ground-state and first excited-state surfaces is found in the D-3h configuration. A detachment mechanism in H- + H-2 collisions related to nonadiabatic transitions between the ground and first excited states is proposed and discussed. (C) 1997 Published by Elsevier Science B.V.