The Auger effect or Auger−Meitner effect is a physical phenomenon in which the filling of an inner-shell vacancy of an

atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas ...

is accompanied by the emission of an

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary partic ...

from the same atom. 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 In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...

. Although most often this energy is released in the form of an emitted

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are Massless particle, massless ...

, the energy can also be transferred to another electron, which is ejected from the atom; this second ejected electron is called an Auger electron.

Effect

The effect was first discovered by

Lise Meitner Elise Meitner ( , ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish physicist who was one of those responsible for the discovery of the element protactinium and nuclear fission. While working at the Kaiser Wilhelm Institute on ra ...

in 1922;

Pierre Victor Auger Pierre Victor Auger (; 14 May 1899 – 24 December 1993) was a French physicist, born in Paris. He worked in the fields of atomic physics, nuclear physics, and cosmic ray physics. He is famous for being one of the discoverers of the Auger effect, ...

independently discovered the effect shortly after and is credited with the discovery in most of the scientific community. Upon ejection, the

kinetic energy In physics, the kinetic energy of an object is the energy that 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 a ...

of the Auger electron corresponds to the difference between the energy of the initial

electronic transition A quantum jump is the abrupt transition of a quantum system (atom, molecule, atomic nucleus) from one quantum state to another, from one energy level to another. When the system absorbs energy, there is a transition to a higher energy level (e ...

into the vacancy and the

ionization energy Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive Electric charge, charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged a ...

for the

electron shell In chemistry and atomic physics, an electron shell may be thought of as an orbit followed by electrons around an atom's Atomic nucleus, nucleus. The closest shell to the nucleus is called the "1 shell" (also called the "K shell"), followed by t ...

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 A Hanford scientist uses an Auger electron spectrometer to determine the elemental composition of surfaces. Auger electron spectroscopy (AES; pronounced in French) is a common analytical technique used specifically in the study of surfaces and, ...

involves the emission of Auger electrons by bombarding a sample with either

X-ray X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...

s or energetic electrons and measures the intensity of Auger electrons that result 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 A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

s. An electron and

electron hole In physics, chemistry, and electronic engineering, an electron hole (often simply called a hole) is a quasiparticle which is the lack of an electron at a position where one could exist in an atom or atomic lattice. Since in a normal atom or ...

(electron-hole pair) can recombine giving up their energy to an electron in the

conduction band In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level, and thus determine the electrical conductivity of the solid. In nonmetals, the valence band is the highest range of electron energies in ...

, increasing its energy. The reverse effect is known as impact ionization. The Auger effect can impact biological molecules such as DNA. Following the K-shell ionization of the component atoms of DNA, Auger electrons are ejected leading to damage of its sugar-phosphate backbone.

Discovery

The Auger emission process was observed and published in 1922 by

, an Austrian-Swedish physicist, as a side effect in her competitive search for the nuclear beta electrons with the British physicist Charles Drummond Ellis. The French physicist

independently discovered it in 1923 upon analysis of a Wilson

cloud chamber A cloud chamber, also known as a Wilson cloud chamber, is a particle detector used for visualizing the passage of ionizing radiation. A cloud chamber consists of a sealed environment containing a supersaturated vapour of water or alcohol. A ...

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. The observation of electron tracks that were independent of the frequency of the incident photon suggested a mechanism for electron ionization that was caused from an

internal conversion Internal conversion is a non-radioactive, atomic decay process where an excited nucleus interacts electromagnetically with one of the orbital electrons of an atom. This causes the electron to be emitted (ejected) from the atom. Thus, in interna ...

of energy from a radiationless transition. Further investigation, and theoretical work using elementary quantum mechanics and transition rate/transition probability calculations, showed that the effect was a radiationless effect more than an internal conversion effect."The Theory of Auger Transitions". Chattarji, D., Academic Press, London, 1976

References

{{X-ray science Atomic physics Foundational quantum physics Electron spectroscopy

Effect

Discovery

See also

References