Electron affinity (data page)

This page deals with the electron affinity as a property of isolated atoms or molecules (i.e. in the gas phase). Solid state electron affinities are not listed here.

Elements

Electron affinity can be defined in two equivalent ways. First, as the energy that is released by adding an electron to an isolated atom (gas phase). (The energy -or electron affinity- is a scalar quantity and the direction of that energy -released- defines a reaction for which the change in energy ΔE is a negative quantity). The electron affinity is also defined in the case of electron capture as E(initial) – E(final) in order to maintain the positive value.^[1] The reverse definition is that the electron affinity is the energy required to remove an electron from a gaseous anion (still a positive quantity, but in which the change in energy ΔE is also a positive quantity). Either convention can be used in practice, but must be consistent in according a scalar, i.e. positive number to the electron affinity.

Negative electron affinities can be used in those cases where electron capture requires energy, i.e. when capture can occur only if the impinging electron has a kinetic energy large enough to excite a resonance of the atom-plus-electron system. Conversely electron removal from the anion formed in this way releases energy, which is carried out by the freed electron as kinetic energy. Negative ions formed in these cases are always unstable. They may have lifetimes of the order of microseconds to milliseconds, but they invariably autodetach after some time. The listed value in the table corresponds to a selected low-lying metastable state, which may or may not be the lowest energy resonance. For example, in He⁻ there is a metastable state with 0.359 ms lifetime at 19.7 eV above the ground state of He, however there is also a lower energy resonance at 19.4 eV that only has a 10⁻¹³ s lifetime.^[2]

Molecules

The electron affinities E_ea of some molecules are given in the table below, from the lightest to the heaviest. Many more have been listed by Rienstra-Kiracofe et al. (2002). The electron affinities of the radicals OH and SH are the most precisely known of all molecular electron affinities.

Bibliography

• Janousek, Bruce K.; Brauman, John I. (1979), "Electron affinities", in Bowers, M. T., Gas Phase Ion Chemistry, 2, New York: Academic Press, p. 53 .
• Rienstra-Kiracofe, J.C.; Tschumper, G.S.; Schaefer, H.F.; Nandi, S.; Ellison, G.B. (2002), "Atomic and molecular electron affinities: Photoelectron experiments and theoretical computations", Chem. Rev., 102, pp. 231–282, doi:10.1021/cr990044u .
• Updated values can be found in the NIST chemistry webbook. These values must be taken with caution, however, for the Electron affinity determinations tables of this webbook show unexplained differences with respect to the original measurements. For instance the electron affinity of the iodine atom is told to be 3.05900(10) eV according to the most precise measurement, despite the fact the original publication^[38] gives 3.0590463(38) eV.

Specific molecules

• Adams, C.L.; Schneider, H.; Ervin, K.M.; Weber, J.M. (2009), "Low-energy photoelectron imaging spectroscopy of nitromethane anions: Electron affinity, vibrational features, anisotropies, and the dipole-bound state", J. Chem. Phys., 130: 074307, doi:10.1063/1.3076892 
• Borshchevskii, A.Ya.; Boltalina, O.V.; Sorokin, I.D.; Sidorov, L.N. (1988), "Thermochemical quantities for gas-phase iron, uranium, and molybdenum fluorides, and their negative ions", J. Chem. Thermodyn., 20 (5): 523, doi:10.1016/0021-9614(88)90080-8 
• Chaibi, W.; Delsart, C.; Drag, C.; Blondel, C. (2006), "High precision measurement of the ³²SH electron affinity by laser detachment microscopy", J. Mol. Spectrosc., 239: 11, doi:10.1016/j.jms.2006.05.012 
• Chowdhury, S.; Kebarle, P. (1986), "Electron affinities of di- and tetracyanoethylene and cyanobenzenes based on measurements of gas-phase electron-transfer equilibria", J. Am. Chem. Soc., 108: 5453, doi:10.1021/ja00278a014 
• Ervin, K.M.; Ho, J.; Lineberger, W.C. (1988), "Ultraviolet photoelectron spectrum of nitrite anion", J. Phys. Chem., 92: 5405, doi:10.1021/j100330a017 
• Ervin, K.M.; Lineberger, W.C. (1991), "Photoelectron spectra of C−
  2 and C₂H⁻", J. Phys. Chem., 95: 1167, doi:10.1021/j100156a026 
• George, P.M.; Beauchamp, J.L. (1979), "The electron and fluoride affinities of tungsten hexafluoride by ion cyclotron resonance spectroscopy", Chem. Phys., 36: 345, doi:10.1016/0301-0104(79)85018-1 
• Goldfarb, F.; Drag, C.; Chaibi, W.; Kröger, S.; Blondel, C.; Delsart, C. (2005), "Photodetachment microscopy of the P, Q, and R branches of the OH⁻(v=0) to OH(v=0) detachment threshold", J. Chem. Phys, 122: 014308, doi:10.1063/1.1824904 
• Huang, Dao-Ling; Dau, Phuong Diem; Liu, Hong-Tao; Wang, Lai-Sheng (2014), "High-resolution photoelectron imaging of cold C−
  60 anions and accurate determination of the electron affinity of C₆₀", J. Chem. Phys., 140: 224315, doi:10.1063/1.4881421 
• Kim, J.B.; Weichman, M.L.; Neumark, D.M. (2015), "Low-lying states of FeO and FeO⁻ by slow photoelectron spectroscopy", Mol. Phys., 113: 2105, doi:10.1080/00268976.2015.1005706 
• Mathur, B.P.; Rothe, E.W.; Tang, S.Y.; Reck, G.P. (1976), "Negative ions from phosphorus halides due to cesium charge exchange", J. Chem. Phys., 65: 565, doi:10.1063/1.433109 
• Mead, R.D.; Lykke, K.R.; Lineberger, W.C.; Marks, J.; Brauman, J.I. (1984), "Spectroscopy and dynamics of the dipole‐bound state of acetaldehyde enolate", J. Chem. Phys., 81: 4883, doi:10.1063/1.447515 
• Miller, T.M.; Leopold, D.G.; Murray, K.K.; Lineberger, W.C. (1986), "Electron affinities of the alkali halides and the structure of their negative ions", J. Chem. Phys., 85: 2368, doi:10.1063/1.451091 
• Nimlos, Mark R.; Ellison, G. Barney (1986), "Photoelectron spectroscopy of sulfur-containing anions (SO−
  2, S−
  3, and S₂O⁻)", J. Phys. Chem., 90: 2574, doi:10.1021/j100403a007 
• Novick, S.E.; Engelking, P.C.; Jones, P.L.; Futrell, J.H.; Lineberger, W.C. (1979), "Laser photoelectron, photodetachment, and photodestruction spectra of O−
  3", J. Chem. Phys., 70: 2652, doi:10.1063/1.437842 
• Page, F. M.; Goode, G. C. (1969), Negative ions and the magnetron, John Wiley & Sons ^[61]
• Ruoff, R.S.; Kadish, K.M.; Boulas, P.; Chen, E.C.M. (1995), "Relationship between the Electron Affinities and Half-Wave Reduction Potentials of Fullerenes, Aromatic Hydrocarbons, and Metal Complexes", J. Phys. Chem., 99: 8843, doi:10.1021/j100021a060 
• Schiedt, J.; Weinkauf, R. (1995), "Spin-orbit coupling in the O−
  2 anion", Z. Naturforsch. A, 50 (11): 1041, doi:10.1515/zna-1995-1110 
• Schiedt, J.; Weinkauf, R. (1999), "Resonant photodetachment via shape and Feshbach resonances: p-benzoquinone anions as a model system", J. Chem. Phys., 110: 304, doi:10.1063/1.478066 
• Schulz, P.A.; Mead, R.D.; Jones, P.L.; Lineberger, W.C. (1982), "OH⁻ and OD⁻ threshold photodetachment", J. Chem. Phys., 77: 1153, doi:10.1063/1.443980 
• Sheps, L.; Miller, E.M.; Lineberger, W.C. (2009), "Photoelectron spectroscopy of small IBr⁻(CO₂)_n(n=0–3) cluster anions", J. Chem. Phys., 131: 064304, doi:10.1063/1.3200941 
• Travers, M.J.; Cowles, D.C.; Ellison, G.B. (1989), "Reinvestigation of the electron affinities of O₂ and NO", Chem. Phys. Lett., 164: 449, doi:10.1016/0009-2614(89)85237-6 
• Troe, J.; Miller, T.M.; Viggiano, A.A. (2012), "Revised electron affinity of SF₆ from kinetic data", J. Chem. Phys., 136: 121102, doi:10.1063/1.3698170 
• Wenthold, P.G.; Kim, J.B.; Jonas, K.-L.; Lineberger, W.C. (1997), "An Experimental and Computational Study of the Electron Affinity of Boron Oxide", J. Phys. Chem. A, 101: 4472, doi:10.1021/jp970645u 
• Zanni, M.T.; Taylor, T.R.; Greenblatt, B.J.; Soep, B.; Neumark, D.M. (1997), "Characterization of the I−
  2 anion ground state using conventional and femtosecond photoelectron spectroscopy", J. Chem. Phys., 107: 7613, doi:10.1063/1.475110 

References

See also