fragmentation reaction

in mass spectrometry
A @[email protected] reaction may be written: \[\text{M}_{1}^{+}\rightarrow \text{M}_{2}^{+}+\text{M}_{3}\] The @[email protected] of a @[email protected] ion of mass-to-charge ratio \(\frac{m_{1}}{z_{1}}\) into an ion of mass-to-charge ratio \(\frac{m_{2}}{z_{2}}\) after electric @[email protected] of the @[email protected] ion and before magnetic deflection gives rise to a peak in the @[email protected] at an apparent mass, \(\frac{m_{2}^{2}\ z_{1}}{m_{1}\ z_{2}^{2}}\). The symbol \(m^{*}\) should be used to indicate the apparent mass of the product ions giving rise to this peak. Traditionally, the peak itself has been called a @[email protected] peak and this should preferably be expressed as @[email protected] peak. It is nevertheless recommended that the former term should be retained. The word @[email protected] should never be used as a noun. Its use as an adjective should be limited to such terms as @[email protected] ion, where it is used correctly, and to the special case of @[email protected] peak discussed above. It should never be used in such terms as @[email protected] reaction, @[email protected] @[email protected], @[email protected] studies, etc. It should be clear that the @[email protected] ion is the ion that undergoes @[email protected]; it is not detected. When a reaction is written with an asterisk above the arrow as shown: \[\text{M}_{1}^{+}\overset{\text{*}}{\rightarrow }\text{M}_{2}^{+}+\text{M}_{3}\] this means that the reaction has been confirmed by the observation of a @[email protected] peak. The textual description of such a process may be written as, for example, (\(m^{*}\), \(43\rightarrow 28\), calcd. 18.2, obsd. 18.3) meaning 'for the @[email protected] \(\frac{m}{z}\ 43\rightarrow \frac{m}{z}\ 28\) a @[email protected] peak at \(\frac{m}{z}\) 18.3 (calculated 18.2) has been observed'.
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 1557 [Terms] [Paper]