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 Core electrons are the electrons in an atom that are not valence electrons and do not participate in chemical bonding. The nucleus and the core electrons of an atom form the atomic core. Core electrons are tightly bound to the nucleus. Therefore, un ...

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