Auger effect

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Auger effect

One of the two principal processes for the relaxation of an inner-shell electron vacancy in an excited or ionized atom. The Auger effect is a two-electron process in which an electron makes a discrete transition from a less bound shell to the vacant, but more tightly bound, electron shell. The energy gained in this process is transferred, via the electrostatic interaction, to another bound electron which then escapes from the atom. This outgoing electron is referred to as an Auger electron and is labeled by letters corresponding to the atomic shells involved in the process. For example, a KLILIII Auger electron corresponds to a process in which an LI electron makes a transition to the K shell and the energy is transferred to an LIII electron (illus. a). By the conservation of energy, the Auger electron kinetic energy E is given by E = E(K) - E(LI) - E(LIII) where E(K,L) is the binding energy of the various electron shells. Since the energy levels of atoms are discrete and well understood, the Auger energy is a signature of the emitting atom. See Electron configuration, Energy level (quantum mechanics)

The other principal process for the filling of an inner-shell hole is a radiative one in which the transition energy is carried off by a photon (illus. b). Inner-shell vacancies in elements with large atomic number correspond to large transition energies and usually decay by such radiative processes; vacancies in elements with low atomic number or outer-shell vacancies with low transition energies decay primarily by Auger processes.

Two principal processes for the filling of an inner-shell electron vacancyenlarge picture
Two principal processes for the filling of an inner-shell electron vacancy
McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.

Auger effect

[ō′zhā i‚fekt]
(atomic physics)
A two-electron process in which an electron makes a discrete transition from a less bound shell to a vacant electron shell and the energy gained in this process is tranferred via the electrostatic interaction to another bound electron which escapes the atom. Also known as Auger transition; internal absorption; internal photoionization.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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More importantly, by studying the thermal stability of the Ba overlayer on the Ni(110) surface, we demonstrate the sensitivity of the low energy Auger electron spectrum to the overlayer order.
In general, the energetic position of an Auger electron peak is a characteristic of the element (i.e., the binding energies of the three electronic states involved) and its chemical state.
Yet, the phase transition from amorphous to ordered barium can induce the following effect: in the amorphous phase the Auger electron emitting atoms have a range of different coordination numbers resulting in slightly shifted and overlapping Auger peaks, causing an effective broadening of the measured spectrum.
The numbers of emitted Auger electrons from a given chemical element are proportional to the concentration of that element at the sample surface.
Detection of the Auger electrons is difficult as scattered primary electrons from the excitation source contribute to a large background in the spectrum.
By building a novel instrument capable of measuring Auger electrons from any angular perspective, the Cincinnati chemists say they have uncovered a more likely origin for the angular distribution of Auger electrons.
They used ADAM to map the angular distribution of silver's Auger electrons. "We used the silver monolayer as the light bulbs and the iodine atoms as the shadow-creating scatterers," Hubbard says.