A theoretical study of the Si22+ dication

Assuming the Born-Oppenheimer approximation, the low-lying electronic spectrum of the doubly charged silicon dimer cation is investigated by multireference configuration interaction methods. Despite of only a relatively small barrier in its ground state 1Σg+ potential energy curve, the lowest vibronic resonances enjoy lifetimes long enough to render Si22+ practically stable against dissociation. The same holds true for the other two metastable equilibria identified for the excited states 13Πuand13Σg-. A comparison with other diatomic dications and the isoelectronic neutral molecule Al2 assists in exposing the characteristics of Si22+.