Template:ASMS types of ions

Transcluded in ASMS 1981 and ASMS 1984

Positive ion

This is an atom, radical, molecule or molecular moiety which has lost one or more electrons thereby retaining an electrically positive charge. The use-of the term cation as an alternative is not recommended. The use of mass ion is not recommended.

Negative ion

An atom, radical, molecule or molecular moiety in the vapor phase which has gained one or more electrons thereby acquiring an electrically negative charge. The use of the term anion as an alternative is not recommended.

Singly-, Doubly-,

Triply-etc. Charged Ion These terms are used to describe an atom, molecule or molecular moiety which has gained or lost one, two, three or more electrons. The term multiply-charged ion is used to refer to ions that have gained or lost more than one electron where the number of electrons lost or gained is not designated.

Parent ion

An electrically charged molecular moiety which may dissociate to form fragment. one or more of which may be electrically charged, and one or more neutral species. A parent ion may be a molecular ion or an electrically charged fragment of a molecular ion.

Fragment ion

An electrically charged dissociation product of an ionic fragmentation. Such an ion may dissociate further to form other electrically charged molecular or atomic moieties of successively lower formula weight. (See also Daughter lon).

Daughter ion

An electrically charged product of reaction of a particular parent ion. In general such ions have a dfrect relationship to a particular precursor ion and indeed may relate to a unique state of the precursor ion. nnThe reaction need not necessarilyinvolve fragmentation. ft could, for example involve a change in the number of charges carried. Thus, all fragment ions are daughter ions but not all daughter ions are necessarilY fragment ions.

Rearrangement ion

An electrically charged dissociation product, involving a molecular or parent ion, in which atoms or groups of atoms have transferred from one portion of a molecule or molecular moiety to another during the fragmentation process.

Stable ion

An ion which is not sufficiently excited to dissociate into a daughter ion and associated neutral fragment(s) or to react further in any other way.

Unstable ion

An ion which is sufficiently excited to dissociate within the ion source.

Metastable ion

An ion which is sufficiently excited to dissociate into a particulardaughter ion and neutral species during the flight from the ion source to the detector. The dissociation is most readily observed when it takes place in one of the field-free regions in a mass spectrometer.

Precursor ion

This term is synonymous with parent ion.

Product ion

This term is synonymous with [daughter ion]].

Molecular ion

An ion formed by the removal (positive ions) or addition (negative ions) of one or more electrons from a molecule without fragmentation of the molecular structure. The mass of lhis ion corresponds to the sum of the masses of the most abundant naturallyoccurring isetopes of the various atoms that make up the molecule (with a correction for the masses of the electrons lost or gained). For example, the mass of the molecular ion of ethyl bromide, C2H5Br will be 2xl2 plus Sxl.0078246 plus 78.n91839 minus the mass of the electron (me)-This is equal to 107.95751 u -mn, u being the unit of atomic mass based on the standard that the mass of the isotope 12c = 12u exactly.

Isotopic molecular ion

A molecular ion containing one or more of the less abundant naturally occurring isotopes of the atoms that make up the molecular structure. Thus, for ethyl bromide there exist molecular isotope ions such as 13CCH5Br+ , C2H4D Br+ C2Hsn81Br+ , 13C2H581Br+ etc. ,

Isotopic ion

Any ion containing one or more of the less abundant naturallynoccurring isotopes of the elements that make up its structure.

Isotopically enriched ions

When the abundance of a particular isotope is increased above the level at which it occurs in nature and is incorporated in a molecule the term "isotopically enriched ion" is used to describe any ion containing the enriched isotope.

Dimeric ion

An ion formed either when a chemical species exists in the vapor phase as a dimer and can be detected as such, or when a molecular ion can attach to a neutral molecule within the ion source to form an ion such as [2M]n+. where M represents the molecule.

Protonated molecule

An ion formed by interaction of a molecule with a proton abstracted from an ion, as often occurs in Chemical Ionization according to the reaction : M + XH⁺ + MH⁺ + X. The symbolism [M+H]⁺ may also be used to represent the protonated molecule.

[Note : The widely-used term 'protonated molecular ion' to "describe the MH+ ion is not recommended. It suggests an association product of a proton with a molecularion]-..

Adduct ion

An ion formed by interaction of two species, usually an ion and a molecule, and often within the ion source, to form an ion containing all the constituent atoms of one species as well as an additional atom or atoms.

Cluster ion

An ion formed by the combination of two or more molecules of a chemical species often in association with a second species. For example, [ (H2OlnHJ + is a cluster ion.

Radical ion

An ion containing an un-paired electron which is thus both an ion and a free radical. The presence of the odd electron is denoted by placing a dot alongside the symbol for the charge. Thus, CzHG+ and SFG- are radical ions.

Odd-electron ion

This term is synonymous .with radical ion.

Even-electron ion

An ion containing nonun-paired electrons, for example CH₃ in its ground state.