Conversion electron

A conversion electron is an electron which results from interactions with metastable atomic nuclei, which results from radioactive decay processes. A metastable nucleus can transfer its energy to an electron that has a certain probability of being in the nucleus. If this happens, the electron becomes a free electron with a kinetic energy equal to the energy of the metastable state minus the binding energy of the electron. This electron is called a conversion electron. Because of its proximity to the nucleus, the conversion electron usually comes from the K shell. The hole in the electron shell is filled by electrons from other shells thus producing a characteristic X-ray peak. The x-ray may then reproduce the effect and cause the emission of an Auger electron.

Competition with gamma decay

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Conversion occurs for the same nuclear decays partly as gamma decay, which hence competes with that process.

Example

In the decay of the nucleus of ¹²⁵I, 7% of the decays emit energy as a gamma ray, while 93% release energy as conversion electrons.