The animation presents an example of beta-delayed particle emission. In this particular case the decay process consists of the following steps:
14355Cs88 → 14356Ba87 + e- + ν,
where ν is the (electron) antineutrino.
The beta-minus decay is followed by neutron emission:
14356Ba87 → 14256Ba86 + n.
In the rollover image of the picture below you can see the decay processes starting from 143Cs. The main branch starting from the first daughter 143Ba is another β- decay process. However, there is also a weak branch (~1.6%) in which the daughter gets rid of the excitation energy of its nucleus by neutron emission rather than by γ emission which is the orthodox way for a decay product to lose excess energy. Note that neutron emission only occurs in 143Ba when it is formed by beta decay. This shows that the excited state of the nucleus is important for the neutron to conquer nuclear force that binds it to the rest of the nucleus.
Neutron decay – in the sense of spontaneous neutron emission by a ground-state nucleus – only occurs near the neutron dripline on the table of nuclides. This type of beta-delayed particle emission, however, is common in nuclear reactors. It is responsible for the production of delayed neutrons the availability of which is very important in reactor control.
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