Electronic structure of (CS₂)₂^-

We investigate theoretically the electronic structure of (CS₂)₂^-. Five different low-lying forms of the anion are identified. These include the ion-molecule complex and a covalently bonded dimer anion, both of which have electronic configurations consistent with electron attachment to the LUMO of the van der Waals dimer. The other species, including the most stable form of the anion, all have cyclic structures and can be viewed as arising from electron capture by cyclic covalently bonded neutral dimers, with electronic configurations doubly excited with respect to the van der Waals dimer. Vertical detachment energies are calculated for the various anions and lead us to reassign the features in the observed photoelectron spectra of (CS₂)₂^-.