(in mass spectrometry)
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
The carbon atoms of the radical
are called the α-, β-, γ-carbons, starting with the atom nearest the functional group.
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
Homolytic cleavage of a bond connecting an atom or group to an excited chromophore. Often applied to a bond connected to a carbonyl group, in which case it is called
a Norrish type I photoreaction.