Section: 10 | Electron Affinities |
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John R. Rumble, ed., CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), CRC Press/Taylor & Francis, Boca Raton, FL.
If a specific table is cited, use the format: "Physical Constants of Organic Compounds," in CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), John R. Rumble, ed., CRC Press/Taylor & Francis, Boca Raton, FL.


Thomas M. Miller

Electron affinity is defined as the energy difference between the lowest (ground) state of the neutral and the lowest state of the corresponding negative ion. The accuracy of electron affinity measurements has been greatly improved since the advent of laser photodetachment experiments with negative ions. Electron affinities can be determined with optical precision, though a detailed understanding of atomic and molecular states and splittings is required to specify the photodetachment threshold corresponding to the electron affinity.Column definitions are as follows.

Column heading Definition
Z Atomic number; given only for atom entries
Mol. form. Atomic or molecular formula; tables for molecular electron affinities are ordered by molecular formula
Name Name of atom or molecule
Elec. aff. Electron affinity, in units of eV
Uncert. Uncertainty of electron affinity value, in units of eV
Method Measurement technique; see table of techniques given below
Ref. Source of electron affinity value

Atomic and molecular electron affinities are discussed in two excellent articles reviewing photodetachment studies which appear in Gas Phase Ion Chemistry, Vol. 3, Bowers, M. T., Ed., Academic Press, Orlando, 1984: Chapter 21 by Drzaic, P. S., Marks, J., and Brauman, J. I., “Electron Photodetachment from Gas Phase Negative Ions,” p. 167, and Chapter 22 by Mead, R. D., Stevens, A. E., and Lineberger, W. C., “Photodetachment in Negative Ion Beams,” p. 213. Persons interested in photodetachment details should consult these articles and the critical reviews of Andersen, T., Haugen, H. K., and Hotop, H., J. Phys. Chem. Ref. Data 28, 1511, 1999, Hotop, H., and Lineberger, W. C., J. Phys. Chem. Ref. Data 14, 731, 1985, and Andersen, T., Haugen, H. K., and Hotop, H. J. Phys. Chem. Ref. Data 28, 1511, 1999. For simplicity in the tables below, any electron affinity that was discussed in the articles by Drzaic et al. or Hotop and Lineberger is referenced to these sources, where original references are given.

The development of cluster-ion photodetachment apparatuses has brought an explosion of electron affinity estimates for atomic and molecular clusters. The policy in this tabulation is to list (in this order) the electron affinities for atoms, diatoms, triatoms, and selected polyatomic molecules and clusters. If the adiabatic electron affinity has been determined for a simple cluster, the value is given, but the reader is referred to original sources for higher-order clusters. Additional data on molecular electron affinities may be found in Lias, S. G., Bartmess, J. E., Liebman, J. F., Holmes, J. L., Levin, R. D., and Mallard, W. G., Gas Phase Ion and Neutral Thermochemistry, J. Phys. Chem. Ref. Data 17, (Supplement No. 1), 1988 and on the NIST WebBook at the Internet address

For the present tabulation, the 2014 CODATA value e/(hc) = 8065.544005 ± 0.000050 cm–1 eV–1 ( has been used to convert electron affinities from the units used in spectroscopic work, cm–1, into eV for this table. Experimental measurements have improved to the level that the 25 ppb uncertainty in e/(hc) will make a difference in a few cases. For this reason, very accurate electron affinities will be given in cm–1 with the relevant references.

Abbreviations used in the tables: calc = calculated value; PT = photodetachment threshold using a lamp as a light source; LPT = laser photodetachment threshold; LPES = laser photoelectron spectroscopy; DA = dissociative attachment; attach = electron attachment/detachment equilibrium; e-scat = electron scattering; kinetic = dissociation kinetics; Knud = Knudsen cell; CT = charge transfer; CD = collisional detachment; and ZEKE = zero electron kinetic energy spectroscopy.

Electron Affinities of Atoms and Molecules

ZMol. form.NameSynonymCAS Reg. No.Elec. aff./eVUncert./eVMethodRef.
Continued on next page...
Atoms (Listed by Atomic Number)
1HHydrogen (atomic)12385-13-60.75420817calc205
HHydrogen (atomic)12385-13-60.7541950.000019LPT89
DDeuterium (atomic)16873-17-90.7545930.000074LPT89
DDeuterium (atomic)16873-17-90.75465629calc205
TTritium (atomic)15086-10-90.75480545calc205
2HeHelium7440-59-7not stablecalc1
4BeBerylliumGlucinium7440-41-7not stablecalc1
7NNitrogen (atomic)17778-88-0not stableDA1
8OOxygen (atomic)17778-80-21.46111350.0000009LPT4
9FFluorine (atomic)14762-94-83.40118970.0000024LPT227
10NeNeon7440-01-9not stablecalc1
12MgMagnesium7439-95-4not stablee-scat1

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