The electronic ground state of the NeAr²⁺ dication. A complete active space SCF/multi-reference CI study

The lowest-lying electronic state of the NeAr²⁺ dication, X ¹Σ⁺, has been investigated using accurate ab initio calculations of the complete active space SCF/multireference CI type employing large one-electron basis sets. A rather deep local minimum is found in the potential energy curve with a barrier of 0.81 eV preventing spontaneous dissociation into the Ne⁺ (²P) + Ar⁺ (²P) separated atom limit, which is 4.46 eV more stable than the metastable NeAr²⁺ diatomic. Thus, the recently experimetally observed NeAr²⁺ dication is most probably the ground state ion. This is in sharp contrast to Ne²⁺ ₂, which is also experimentally known, but since its X ¹Σ⁺ electronic ground state potential is purely repulsive must be in a long-lived excited state.