A new class of free stable doubly negative systems: Three Si2O52- isomers and their interconversion

The free dianionic Si2O52- system is studied by standard ab initio methods. We have located three distinct isomers in the Si2O52- system. All three Si(2)O(5)2(-) isomers are found to be thermodynamically stable with respect to dissociation into monoanionic fragments. However, only two of them are predicted to be clearly stable with respect to vertical electron autodetachment. Minimal energy pathways which interconnect the three isomers have been studied together with the binding energy of the excess electron along them. The results give rise to an unusual nuclear dynamics problem. In particular, the associated barriers have been found to be high and wide enough to predict long lifetimes for two free dianionic species. (C) 1996 American Institute of Physics.