Auger electron

See also: Auger

The electrons Auger are electrons emitted at the time of the de-energizing of a Atome. This phenomenon was discovered in 1923 by Lise Meitner but it is Pierre Auger which was also interested in the phenomenon a few years later which gave him its name.

When an atom is bombarded by X-rays or electrons of strong energy, it can occur an ionization by photoelectric Effet and a electron of a deep layer is ejected, the atom is in an excited state.

The atom is de-energized by an electronic transition: an outer-shell electron goes down and comes to occupy the left place vacuum. This transition causes the emission of energy which can take two forms:

  • a Photon X, it is the x-ray fluorescence
  • an outer-shell electron is ejected, it is a Auger electron.
This phenomenon is used to make ultimate analyzes of surface: it is the spectrometry Auger .

Auger spectrometry

A Auger spectrometer is an apparatus very similar to a Electron microscope with sweeping; besides it makes it possible to make images of the type MEB, although of bad quality.

The apparatus comprises an electron gun which bombards the sample, and a detector of electrons which detects the Auger electrons and determines their energy. The energy of the electrons makes it possible to determine the chemical nature of the atoms, and the sweeping mode makes it possible to draw up a chemical cartography of the surface of the sample.

The Auger electrons having a weak energy, only those coming from the first atomic layers leave the sample, it is thus a surface method of analysis. For the same reason, it is necessary to work in high vacuum (ultra vacuum, about 10-8 Pa, 10-10 Torr).

In addition, in fact the light elements (weak Atomic number Z ) produce the most electrons Auger, heavy atoms (high Z ) producing photons X especially. chemical analysis is thus limited to the light elements.

See too

Internal bonds

External bonds

  • Spectroscopy of the Auger electrons, Technical of the engineer

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