The '''Auger effect''' ({{pronEng|ˈɔːʒɚ}}, or Oh' jeh) is a phenomenon in [[physics]] in which the emission of an [[electron]] from an [[atom]] causes the [[Secondary emission|emission of a second electron]].<ref>{{GoldBookRef|title=Auger effect|url=http://goldbook.iupac.org/A00520.html}}</ref> When an [[electron]] is removed from a core level of an [[atom]], leaving a vacancy, an electron from a higher energy level may fall into the vacancy, resulting in a release of [[energy]]. Although sometimes this energy is released in the form of an emitted [[photon]], the energy can also be transferred to another electron, which is ejected from the atom. This second ejected electron is called an '''Auger electron'''.<ref>{{GoldBookRef|title=Auger electron|url=http://goldbook.iupac.org/A00521.html}}</ref>

Upon ejection the [[kinetic energy]] of the Auger electron corresponds to the difference between the energy of the initial [[electronic transition]] and the [[ionization energy]] for the [[electron shell]] from which the Auger electron was ejected. These energy levels depend on the type of atom and the chemical environment in which the atom was located. [[Auger electron spectroscopy]] involves the emission of Auger electrons by bombarding a sample with either [[X-ray]]s or energetic electrons and measures the intensity of Auger electrons as a function of the Auger electron energy. The resulting spectra can be used to determine the identity of the emitting atoms and some information about their environment. [[Auger recombination]] is a similar Auger effect which occurs in [[semiconductor]]s. An electron and [[electron hole]] (electron-hole pair) can recombine giving up their energy to an electron in the conduction band, increasing its energy. The reverse effect is known as [[impact ionization]].

The name "Auger effect" comes from one of its discoverers, [[Pierre Victor Auger]], and not from the similarly-named device, the [[auger]].

== Discovery ==
The Auger emission process was discovered in the 1920s by [[Lise Meitner]], an Austrian physicist. The Auger effect was discovered in 1925 by [[Pierre Victor Auger]] upon analysis of a Wilson [[cloud chamber]] experiment. High energy X-rays were applied to ionize gas particles and observe [[photoelectric]] electrons. Observation of electron tracks independent of the frequency of the incident photon energy suggested a mechanism for electron ionization that was caused from an [[internal conversion]] of energy of from a radiationless transition. Further investigation and theoretical work showed that the effect was a radiationless effect more than an internal conversion effect by use of elementary quantum mechanics and transition rate and transition probability calculations. (ref 1)

== See also ==
*[[Carrier generation and recombination|Charge carrier generation and recombination]]
*[[Auger electron spectroscopy]]

== References ==
*"The Auger Effect and Other Radiationless Transitions". Burhop, E.H.S., Cambridge Monographs on Physics, 1952
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[[Category:Atomic physics]]
[[Category:Foundational quantum physics]]

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