Energy required to detach an electron from the singly charged negative ion (energy for the process E01977-1.png). The equivalent more common definition is the energy released (\(E_{\textrm{initial}}- E_{\textrm{final}}\)) when an additional electron is attached to a neutral atom or molecule.
Green Book, 2nd ed., p. 20 [Terms] [Book]
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 1546 [Terms] [Paper]
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1109 [Terms] [Paper]