Metastable states in the Karslruhe Nuclide Chart

July 24th, 2019
by Joseph Magill

Qu. (from M. R. KTE Karlsruhe, Germany):
Dear Nucleonica Team,
I have always wondered what the criteria are to show the metastable state of a nuclide on the chart. The first guess would be the half life of the state. But I found for example the nuclide Rn-214 which shows a metastable state of only 0,69 ns. Is there an arbitrary threshold just below that number where you show the state on the chart if it is above? If the threshold depends on the half life, is there a scientific reason for that threshold? Are all states shown that are above that threshold?
Rn214Ans. (Nucleonica Team)
Metastable states, which do not undergo alpha or beta decays or spontaneous fission, i.e. decay only by isomeric transition are shown (usually) only if their half-life is larger than 1 s (to save space).

Rn 214 excited states Rn 214m and Rn 214n have been observed, both with alpha decay to Po 210. Although their half-lives are less than 1s they are shown in KNC. In this way the users of KNC can know that the alpha emission is not from the ground state of Rn 214 and can have higher energy than the Q-value of ground state to ground state decay.
In some particular cases when the metastable state has an important role in a decay chain or in nuclear physics theory, it is presented even it decays only with isomeric transition and has a half-life shorter than 1s.
There is an interesting article on wikipedia.

Posted in FAQs, Karlsruhe Nuclide Chart | Comments (0)

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