Dication

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A dication is any cation, of general formula ²⁺, formed by the removal of two electrons from a neutral species.

Diatomic dications corresponding to stable neutral species (e.g. H₂²⁺ 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).

An example of a stable diatomic dication which is not formed by oxidation of a neutral diatomic molecule is the dimercury dication Hg₂²⁺. An example of a polyatomic dication is S₈²⁺, formed by oxidation of S₈ and unstable with respect to further oxidisation over time to form SO₂.