1. The fission of a bond originating at an atom which is adjacent to one assumed to bear the charge; the definition of β-, γ-cleavage then follows automatically. The process:
    would thus be described as α-fission of a ketone with expulsion of a radical R1·. The carbon atoms of the radical R1· are called the α-, β-, γ-carbons, starting with the atom nearest the @F02555@.
    PAC, 1991, 63, 1541. (Recommendations for nomenclature and symbolism for mass spectroscopy (including an appendix of terms used in vacuum technology). (Recommendations 1991)) on page 1558 [Terms] [Paper]
  2. Homolytic cleavage of a bond connecting an atom or group to an excited @C01076@. Often applied to a bond connected to a carbonyl group, in which case it is called a @N04219@.
    This reaction should be distinguished from an @A00007@.
    PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 302 [Terms] [Paper]