Abstract :
Electronic states associated with the low-lying Born-Oppenheimer spectrum and crucial for the stability and experimental observability of the doubly positively charged carbon system C22+ are studied by ab initio methods. This includes computation of potential energy curves and transition moments by multireference configuration interaction methods, and an investigation of the corresponding vibrational resonance levels and lifetimes. By analogy with the electronic ground state X3∑g− of the isoelectronic neutral molecule B2, the lowest potential energy curve of C22+ that supports quasibound vibronic motion belongs to the state 1 3∑g−. In case of C22+, however, this state is destabilized by a crossing with the repulsive potential energy curve of 13Πu, and the induced electronic transitions represent the major decay channel of C22+ (1 3∑g−). Also the quintet state 1 5∑g− is quasibound; whereas most of its vibronic levels are practically stable against dissociative tunneling interactions with other electronic states furnish the principal decay mechanism for 1 5∑u−. Additional bonding and stability propertie of C22+ are exposed by monitoring the behaviour of potential energy curves while rising the nuclear charge from the neutral to the doubly positively charged situation.
