When does electron capture emit gamma rays?

1 Answer
Jun 22, 2016


No gamma rays are emitted in electron catpure.


Electron capture (EC) is a process that competes with positron (#beta^+#) emission. In EC the unstable nucleus captures an orbital electron, usually from the shell closest to the nucleus (K-shell). The nucleus emits a #color(blue)"neutrino"#.

EC leaves a vacancy in the shell from which the electron was captured. This can be filled with electrons dropping down from a higher-level. This releases energy in the form of a photon classified as #color(blue)"characteristic X-ray"#. It is also possible that the energy is not emitted as a photon, but is transfered to another electron in a higher shell. The emitted electron in this process is called an #color(blue)"Auger electron"#.

Note that although gamma rays and X-rays are both photons, they are not the same. Gamma rays originate from processes in the nucleus en X-rays originate from the surrounding electron shells.