Unimolecular decompositions of even‐electron ions

Fragmentations of even‐electron ions of lifetimes ≥10 −5 s caused by electron and chemical ionization and by collisional activation have been correlated. Proposed reaction classifications include: cleavage of one bond with charge migration; cleavage of one bond through cyclization‐displacement; cleavage of two bonds in a cyclic ion with charge retention; and cleavage of two bonds in an acyclic ion with rearrangement and charge retention. Such reactions are compared with those of odd‐electron ions; despite a higher tendency for rearrangement, the decompositions of a positive even‐electron ion, in particular as displayed in its collisional activation spectrum, have substantial utility for characterizing its structure.