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Auger electron spectroscopy

Auger electron spectroscopy is an analytical technique in surface chemistry and materials science.

Auger electron spectroscopy probes the chemistry of a surface by measuring the energy of electrons emitted from that surface when it is irradiated with electron of energy in the range 2 - 50 keV. Some of the electrons emitted from the surface have energies characteristic of the element from which they were emitted, and in some cases, the bonding state of those atoms. The physical process by which these electrons are made is called the Auger effect.

This effect was discovered independently by both Lise Meitner and Pierre Auger[?] in the 1920's. Though the discovery was made and reported by Meitner in 1923 in the Journal Zeitschrift fur Physik, two years before Auger discovered the effect, the English speaking scientific community came to attach Auger's name to it, perhaps because of the political climate of Europe at the time, perhaps because of sexism.

The Auger effect occurs because the incident electrons can remove a core state electron from a surface atom. This core state can be filled by an outer shell electron from the same atom, in which case the electron moves to a lower energy state, and the energy associated with the transition is the difference in orbital energies. This energy must be released in some fashion. In some cases this energy is imparted to a second outer shell electron, which then is ejected from the atom. The characteristic energy of this ejected electron is

     ECore State - (ES1 + ES2 )

where S1 and S2 are the outer shell states. Because these orbital energies are determined by the element of the atom, the composition of a surface can be measured.

Auger electron spectroscopy is useful as a surface analytical technique because the energies of the electrons emitted are typically in the range of 50 eV to 3 keV, and at this energy they cannot escape from more than a few nanometers deep in the surface ( of course, the higher the energy, the thicker the layer from which they can escape. The technique is commonly used in conjunction with another technique like scanning electron microscopy (SEM) or low energy electron diffraction (LEED).

Auger is pronounced so as to rhyme with "OJ", but with the softer G associated with French pronunciation.



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