Internal conversion

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Nuclear processes
Radioactive decay processes
Alpha decay
Beta decay
Cluster decay
Double beta decay
Double electron capture
Electron capture
Gamma radiation
Internal conversion
Isomeric transition
Neutron emission
Positron emission
Proton emission
Spontaneous fission
Nucleosynthesis
Neutron Capture
* The R-process
* The S-process
Proton capture:
* The P-process
* The Rp-process
Spallation

Nuclear processes
Radioactive decay processes Alpha decay Beta decay Cluster decay Double beta decay Double electron capture Electron capture Gamma radiation Internal conversion Isomeric transition Neutron emission Positron emission Proton emission Spontaneous fission Nucleosynthesis Neutron Capture * The R-process * The S-process Proton capture: * The P-process * The Rp-process Spallation

This article is about the nuclear process. For the chemical process, see Internal conversion (chemistry).

Internal conversion is a radioactive decay process where an excited nucleus interacts with an electron in one of the lower electron shells causing the electron to be emitted. This is not to be confused with a photoelectric effect where a photon emitted from the nucleus interacts with the electron.

The internal conversion process is not actually the photoelectric ejection of an atomic electron, as the nucleus does not actually emit a gamma ray in the first place in this process. What happens is that the wavefunction of an inner shell electron penetrates the nucleus (ie there is a finite probability of the electron being found in the nucleus) and when this is the case the electron takes the energy of the nuclear transition without an intermediary gamma ray being produced. The energy of the emitted electron is equal to the transition energy minus the binding energy of the electron. Most internal conversion electrons come from the K shell as this electron has the highest probability of being found inside the nucleus.

After the electron has been emitted, the atom is left with a vacancy in one of the inner electron shells. This hole will be filled with an electron from one of the higher shells and subsequently a characteristic x-ray or Auger electron will be emitted.

Internal conversion is favoured when the energy gap between nuclear levels is small, and is also the only mode of de-excitation for 0+ -> 0+ (i.e. E0) transitions. It is the predominant mode of de-excitation whenever the initial and final spin states are the same, but the multi-polarity rules for nonzero initial and final spin states do not necessarily forbid the emission of a gamma ray in such a case.

The tendency towards internal conversion can be determined by the internal conversion coefficient, which is empirically determined by the ratio of de-excitations that go by the emission of electrons to those that go by gamma emission.

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[HyperPhysics]

Internal conversion

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