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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
e
0
0
1
0
0
1-
1
1
n e p
ν+ ⇒ +
+
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.