Theoretical investigations of small multiply charged cations. II. CNe ⁿ⁺ (1≤n≤4)

Extended MCSCF calculations of the CASSCF type have been performed for the energetically lowest-lying electronic states of CNe⁺, CNe ²⁺, CNe³⁺, and CNe⁴⁺. Whereas the mono- and tetracations exhibit essentially repulsive potential curves, the CNe ²⁺ dication is predicted to be a kinetically stable ion. The computed barrier to dissociation for the X¹Σ⁺ state of CNe²⁺ amounts to 1.62 eV, and for the a ³Π state a potential well of 0.80 eV depth is calculated. The CNe²⁺ dication is therefore predicted to be experimentally observable in the gas phase. Also the CNe³⁺ trication is calculated to exhibit a small minimum in its X ²Σ⁺ state. Bonding in these unusual cations is discussed and compared to known isoelectronic species.