Beta delayed processes

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Beta Delayed Processes

To the right of the line of stability, the nuclides are neutron rich and neutron emission can be expected in this region by analogy with proton emission from proton rich nuclides. Through the \beta decay process, the daughter nuclide is formed in an excited state which is unstable against particle emission. The characteristic timescale of this particle emission process is that of the \beta decay of the parent.


Beta Delayed Neutron Emission

Neutron emission immediately following \beta- emission (beta delayed neutron emission denoted \betan) has been observed in many neutron-rich nuclides. The phenomena of delayed neutron emission is very important in the control of nuclear reactors since neutron emission occurs on a timescale much longer than that associated with fission – this allows a response time long enough to move control rods and thereby control the fission reactor. An example of this type of emission is given by N17 i.e.

Betan.png


where the asterisk denotes the short-lived intermediate excited states of oxygen-17. The effective half-life for this process is 4.17 s.


Beta Delayed Alpha Emission Some nuclides in the light-element region beta decay partly to excited states which are unstable with respect to emission of an alpha particle (\beta\alpha). Both the positron decay from boron-8 and negatron decay from lithium-8 (\beta 2\alpha) are beta-delayed alpha emission, because ground as well as excited states of beryllium-8 are unstable with respect to breakup into two alpha particles. Another example is the decay of Na20, i.e.

Betaa.png



Beta Delayed Proton Emission

In many cases, positron decay leads to an excited nuclear state not able to bind a proton. One example of this is the decay of Te111, i.e.

Betap.png


In addition to \betan, \beta\alpha, \betap described above, \betad, \betat, \betasf have also been observed.

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