The animation presents an example of beta-delayed particle emission. In this particular case the decay process consists of the following steps:
3217Cl15 → 3216S16 + e+ + ν,
Note that the ground state of 32S is stable making up 95% of sulfur in nature. However some of the excited daughter nuclei undergo alpha emission (α decay) ending up as stable 28Si , which is the major natural isotope of silicon (abundance: 92%):
3216S16 → 2814Si14 + 42He2.
|In the rollover image of the picture below you can see the decay processes starting from 32Cl. The main branch is simple β+ decay (denoted by ε in the chart) that stops at 32S. But a thin branch (representing 5 cases out of 10 000) goes on because the daughter nucleus gets rid of its high excitation energy by emitting an α particle rather than a γ photon. Since the process is very rare we could consider it unimportant if we did not know that the 32S isotope of sulfur that suffers α decay here is absolutely stable at least in its ground state. Moreover, as we can see in the figure further below , the binding energy per nucleon (B/A) is higher for the decaying chlorine isotope than for the silicon isotope formed, and therefore the decay would never occur were it not for the high excitation energy. Note that α decay (a spontaneous process) is typical of much heavier nuclides that have relatively low neutron to proton ratio.|
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