The characteristics of doubly and triply charged ions C²⁺₂, C^2-₂ and C³⁺₂

Based on group theory and atomic and molecular reaction statics, this paper derives the possible electronic states of C^2+_2, C^2-_2 and C^3+_2, and their reasonable dissociation limits and determines their ground electronic states C^2+_2(X^3\Sigma_\rm u), C^2-_2(X^1\Sigma^+_\rm g) and C^3+_2(X^4\Sigma^-_\rm u) using quantum mechanical calculations at the level of QCISD/6-311G^*. All the potential energy curves of their ground states have both a minimum and a maximum, which are the so-called "energy trapped" molecules. This sort of potential maximum is chiefly due to Coulomb repulsion. We propose the perturbation effect of ionic charges, which is used to explain why the orbital degeneracy of diatomic ions may be removed. The characteristics of potential curves for diatomic ions are briefly described.