electron ionization

in mass spectrometry

This is the term used to describe ionization of any species by electrons. The process may, for example, be written:

for atoms or molecules:
$M + e → M + · + 2 e$
for radicals:
$M · + e → M + + 2 e$

The term 'electron impact' should not be used.

See: radical ion for a note concerning the symbolic representation of radical ions;

See also: photoionization

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 1547