Auger electron

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Auger emission (pronounced /ˡɔːʒɚ/) is a phenomenon in physics in which the emission of an electron from an atom causes the emission of a second electron. This second ejected electron is called an Auger electron.

The name Auger electron comes from one of its discoverers, Pierre Victor Auger. The name does not come from the similarly-named device, the auger.

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 then ejected from the atom.

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 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-rays 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 semiconductors. 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.

There are two international committees that write standards on Auger electron spectroscopy. They are the ASTM (American Society for Testing Materials International) committee E42 and the ISO (International Standards Organization) technical committee TC-201.

[edit] History

The Auger emission process was discovered in the 1920s by Lise Meitner, an Austrian physicist. Subsequently Pierre Victor Auger, a French Physicist, also discovered the process. Auger reported the discovery in the journal Radium in 1925 and it was Auger who had the process named after him.