Auger electron
Encyclopedia
The Auger effect is a physical phenomenon in which the transition of an electron
in an atom
filling in an inner-shell vacancy causes the emission of another electron. When a core electron
is removed, 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, after one of its discoverers, Pierre Victor Auger
.
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
.
, an Austrian physicist, as a side effect in her competitive search for the nuclear beta electrons with the British physicist Charles Drummond Ellis
. The French physicist Pierre Victor Auger
also discovered it in 1923 upon analysis of a Wilson cloud chamber
experiment and it became the central part of his PhD work. 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 suggested a mechanism for electron ionization that was caused from an internal conversion
of energy 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.
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
in an atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
filling in an inner-shell vacancy causes the emission of another electron. When a core electron
Core electron
Core electrons are the electrons in an atom that are not valence electrons and therefore do not participate in bonding. An example: the carbon atom has a total of 6 electrons, 4 of them being valence electrons. So the remaining 2 electrons must be core electrons.They are so tightly bound to the...
is removed, leaving a vacancy, an electron from a higher energy level may fall into the vacancy, resulting in a release of energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
. Although sometimes this energy is released in the form of an emitted photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
, the energy can also be transferred to another electron, which is ejected from the atom. This second ejected electron is called an Auger electron, after one of its discoverers, Pierre Victor Auger
Pierre Victor Auger
Pierre Victor Auger was a French physicist, born in Paris. He worked in the fields of atomic physics, nuclear physics, and cosmic ray physics....
.
Upon ejection the kinetic energy
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
of the Auger electron corresponds to the difference between the energy of the initial electronic transition and the ionization energy
Ionization energy
The ionization energy of a chemical species, i.e. an atom or molecule, is the energy required to remove an electron from the species to a practically infinite distance. Large atoms or molecules have a low ionization energy, while small molecules tend to have higher ionization energies.The property...
for the electron shell
Electron shell
An electron shell may be thought of as an orbit followed by electrons around an atom's nucleus. The closest shell to the nucleus is called the "1 shell" , followed by the "2 shell" , then the "3 shell" , and so on further and further from the nucleus. The shell letters K,L,M,.....
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
Auger electron spectroscopy
Auger electron spectroscopy is a common analytical technique used specifically in the study of surfaces and, more generally, in the area of materials science...
involves the emission of Auger electrons by bombarding a sample with either X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
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
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
s. An electron and electron hole
Electron hole
An electron hole is the conceptual and mathematical opposite of an electron, useful in the study of physics, chemistry, and electrical engineering. The concept describes the lack of an electron at a position where one could exist in an atom or atomic lattice...
(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
Impact ionization
Impact ionization is the process in a material by which one energetic charge carrier can lose energy by the creation of other charge carriers...
.
Discovery
The Auger emission process was discovered in 1922 by Lise MeitnerLise Meitner
Lise Meitner FRS was an Austrian-born, later Swedish, physicist who worked on radioactivity and nuclear physics. Meitner was part of the team that discovered nuclear fission, an achievement for which her colleague Otto Hahn was awarded the Nobel Prize...
, an Austrian physicist, as a side effect in her competitive search for the nuclear beta electrons with the British physicist Charles Drummond Ellis
Charles Drummond Ellis
Sir Charles Drummond Ellis was a physicist and scientific administrator. His work on the magnetic spectrum of the beta-rays helped to develop a better understanding of nuclear structure....
. The French physicist Pierre Victor Auger
Pierre Victor Auger
Pierre Victor Auger was a French physicist, born in Paris. He worked in the fields of atomic physics, nuclear physics, and cosmic ray physics....
also discovered it in 1923 upon analysis of a Wilson cloud chamber
Cloud chamber
The cloud chamber, also known as the Wilson chamber, is a particle detector used for detecting ionizing radiation. In its most basic form, a cloud chamber is a sealed environment containing a supersaturated vapor of water or alcohol. When a charged particle interacts with the mixture, it ionizes it...
experiment and it became the central part of his PhD work. 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 suggested a mechanism for electron ionization that was caused from an internal conversion
Internal conversion
Internal conversion is a radioactive decay process where an excited nucleus interacts with an electron in one of the lower atomic orbitals, causing the electron to be emitted from the atom. Thus, in an internal conversion process, a high-energy electron is emitted from the radioactive atom, but...
of energy 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.
See also
- Auger electron spectroscopyAuger electron spectroscopyAuger electron spectroscopy is a common analytical technique used specifically in the study of surfaces and, more generally, in the area of materials science...
- Coster–Kronig transition
- Electron captureElectron captureElectron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
- Radiative Auger effectRadiative Auger effectRadiative Auger effect is a decay channel of an inner-shell atomic vacancy state, in which an x-ray photon is emitted accompanying simultaneous promotion of an electron into either a bound or a continuum state. Thus the transition energy is shared between the photon and the electron.The effect was...
- Charge carrier generation and recombinationCarrier generation and recombinationIn the solid state physics of semiconductors, carrier generation and recombination are processes by which mobile charge carriers are created and eliminated. Carrier generation and recombination processes are fundamental to the operation of many optoelectronic semiconductor devices, such as...