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.
|Common element dications|
Some metals are commonly found in the form of dications when in the form of salts, or dissolved in water. Examples include the alkaline earth metals, Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Ra2+, later transition metals V2+, Cr2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and the heavy members of the carbon group Sn2+ and Pb2+.