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(2009), "Low-energy photoelectron imaging spectroscopy of nitromethane anions: Electron affinity, vibrational features, anisotropies, and the dipole-bound state", J. Updated values can be found in the NIST chemistry webbook for around three dozen elements and close to 400 compounds.(2002), "Atomic and molecular electron affinities: Photoelectron experiments and theoretical computations", Chem. (ed.), Gas Phase Ion Chemistry, 2, New York: Academic Press, p. 53. (1979), "Electron affinities", in Bowers, M. NIST chemistry webbook after Borshchevskii et al. The electron affinities of the radicals OH and SH are the most precisely known of all molecular electron affinities. Many more have been listed by Rienstra-Kiracofe et al. The electron affinities E ea of some molecules are given in the table below, from the lightest to the heaviest. They may have lifetimes of the order of microseconds to milliseconds, and invariably autodetach after some time. Negative ions formed in these cases are always unstable. Conversely electron removal from the anion formed in this way releases energy, which is carried out by the freed electron as kinetic energy. 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.
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Negative electron affinities can be used in those cases where electron capture requires energy, i.e. The latter can be regarded as the ionization energy of the –1 ion or the zeroeth ionization energy. The second (reverse) definition is that electron affinity is the energy required to remove an electron from a singly charged gaseous negative ion. First, as the energy that is released by adding an electron to an isolated gaseous atom. Analogically, it is possible to define the electron affinity for chemical compounds (molecules).Electron affinity can be defined in two equivalent ways.Electronic affinity is measured (or calculated theoretically) for isolated atoms in gaseous state.This is the case, for example, in the case of sodium-chlorine (Na-Cl) bonding in sodium chloride. When this difference is large enough, the electron is virtually transferred from one atom to the other creating an ionic bond. When two atoms form a chemical compound, the electron cloud is shifted towards the element with a higher electron affinity.However, it may be slightly different for individual isotopes. Electronic affinity is a property specific to a given element.Such calculations can be made using quantum chemistry methods. Theoretically, the value of the electron affinity can be approximated using Koopmans theorem as energy of lowest unocuppied orbital.The electronic affinity is most often given in electron volts (eV) or in kilojoules per mole (kJ / mol).Simply speaking, the greater the affinity of electrons, the more eagerly the atoms of a given element join electrons to form ions (anions). Electron affinity is related to electronegativity of elements.As a result of such attachment, a negative ion (anion) is formed. The electronic affinity is amount of energy, that is released during the attachment of the electron to the neutral atom.