A
fragmentation reaction may be written:
The
decomposition of a
metastable ion of mass-to-charge ratio
into an ion of mass-to-charge ratio
after electric
acceleration of the
metastable ion and before magnetic deflection gives rise to a peak in the
mass spectrum at an apparent mass,
. The symbol
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
metastable peak and this should preferably be expressed as
metastable ion peak. It is nevertheless recommended that the former term should be retained. The
word
metastable should never be used as a noun. Its use as an adjective should be limited to such
terms as
metastable ion, where it is used correctly, and to the special case of
metastable peak discussed above. It should never be used in such terms as
metastable reaction,
metastabledecomposition,
metastable studies, etc. It should be clear that the
metastable ion is the ion that undergoes
fragmentation; it is not detected. When a reaction is written with an asterisk above the arrow
as shown:
this means that the reaction has been confirmed by the observation of a
metastable peak. The textual description of such a process may be written as, for example,
(
,
, calcd. 18.2, obsd. 18.3) meaning '
for the fragmentation
a metastable peak at
18.3 (calculated 18.2) has been observed'.
Source:
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
