Electron capture

Electron Capture (denoted $\epsilon$ or ec)

Neutron deficient nuclides can also attain stability by capturing an electron from the inner K orL shells of the atomic orbits. As a result, a proton in the nucleus transforms to a neutron i.e.

$p + e^- \to n + \nu$

The process is similar to $Î²^+$ decay in that the charge of the nucleus decreases by 1. The ed decay process can be described by:

ec decay: $_Z^AP \to _{Z-1}^AD^* + \nu$

and the daughter is usually produced in an excited state $D^*$. The resulting nucleus is unstable and decays by the ejection of a neutrino (ν) and the emission of an X-ray when the electron vacancy in the K or L shell is filled by outer orbital electrons.

Reference