Editing Ion source (section)

===Electron capture ionization===
Electron capture ionization (ECI) is the ionization of a gas phase [[atom]] or [[molecule]] by attachment of an [[electron]] to create an ion of the form A<sup>−•</sup>. The reaction is

:<chem>A + e^- ->[M] A^-</chem>

where the M over the arrow denotes that to conserve [[energy]] and [[momentum]] a third body is required (the [[molecularity]] of the reaction is three).

Electron capture can be used in conjunction with [[chemical ionization]].<ref>{{Citation | doi = 10.1021/ac50035a017 | title = Electron capture negative ion chemical ionization mass spectrometry | year = 1978 |author1=Donald F. Hunt |author2=Frank W. Crow | journal = Analytical Chemistry | volume = 50 | issue = 13 | pages = 1781–1784}}</ref>

An [[electron capture detector]] is used in some [[gas chromatography]] systems.<ref>{{GoldBookRef|title=electron capture detector (in gas chromatography)|file= E01981}}</ref>