CPB Budapest 2017

Radioactive Decay

Electron Capture (EC)

A second possibility for unstable nuclides having an excessive number of protons in comparison to neutrons to be transformed to stable nuclides is the electron capture (EC). Electron capture is an alternative decay scheme for such nuclides to the β + decay which requires that the parent atom has an excess energy (mass) of at least 1.022 MeV in order to be able to undergo such a β + decay scheme. The basic transformation process behind the electron capture is

1 1

0

1

0 0

n e p ν+ ⇒ +

+

1-

0

e

An orbital electron of the parent atom is captured by the nucleus. Candidates for the electron capture process are orbit electrons from any of the orbit shells K, L, M, etc. Practically electrons from the K shell are mostly involved due to their close neighbourhood to nucleus. In dependence on the origin of the involved electron the electron capture process is called K capture, L capture, etc.