# Electron capture ionization

Electron capture ionization is the ionization of a gas phase atom or molecule by attachment of an electron to create an ion of the form A–•. The reaction is

$A + e^- \overset{M}{\to} A^-$

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.[1]

An electron capture detector is used in some gas chromatography systems.[2]