Dications
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). The He2+
2 dication is kinetically stable.
An example of a stable diatomic dication which is not formed by oxidation of a neutral diatomic molecule is the dimercury dication Hg2+
2. An example of a polyatomic dication is S2+
8, formed by oxidation of S8 and unstable with respect to further oxidisation over time to form SO2.
Many organic dications can be detected in mass spectrometry for example CH2+
4 (a CH2+
2·H
2 complex) and the acetylene dication C
2H2+
2. The adamantyl dication has been synthesized. 
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