The structure of a weakly bound ionic trimer: Calculations for the (He2H-)-He-4 complex

The weakly bound diatomic systems He-4(2) and (HeH-)-He-4 have been found a ble to support only one bound state for J=0, although the latter also suppo rts an additional bound state for J=1. In the present paper we, therefore, study the structure of the bound states which might exist for the weakly bo und triatomic (He2H-)-He-4, in its J=0 state, by describing the full potent ial as a simple addition of two-body (2B) interactions. We carry out bound state calculations using both Jacobi coordinates within a discrete variable representation (DVR) and pair coordinates with a distributed Gaussian func tion (DGF) expansion. The system is shown to possess two bound states with respect to its lower dissociation threshold and two further "ghost" states before the complete break-up threshold. The spatial structures of such stat es and of the floppy complex are analyzed in detail, as is the possibility of detecting Efimov-type states in such a weakly bound aggregate. Finally, the inclusion of three-body (3B) forces in the description of the full inte raction and its effect on the number of possible bound states is also discu ssed. (C) 2001 American Institute of Physics.