A dication is any cation, of general formula X2+, formed by the removal of two electrons from a neutral species.
Diatomic dications corresponding to stable neutral species (e.g. H2+2 formed by removal of two electrons from H2) often decay quickly into two singly charged particles (H+), due to the loss of electrons in bonding molecular orbitals.
Energy levels of diatomic dications can be studied with good resolution by measuring the yield of pairs of zero-kinetic-energy electrons from double photoionization of a molecule as a function of the photoionizing wavelength (threshold photoelectrons coincidence spectroscopy – TPEsCO).
However, molecular dications, in particular CO22+, have never been observed so far though predicted to be present for instance at Mars.
[3] Indeed, this ion by means of its symmetry and strong double bounds is more stable (longer lifetime) than other dications.