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User:Awc/Changing decay rates

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Changing decay rates

Wikipedia: Changing decay rates

The radioactive decay modes of [1] and [2] are known to be slightly sensitive to chemical and environmental effects which change the electronic structure of the atom, which in turn affects the presence of 1s and 2s electrons which participate in the decay process. A small number of mostly light nuclides are affected. For example [3] can affect the rate of electron capture to a small degree (generally less than 1%) depending on the proximity of electrons to the nucleus in beryllium. In 7Be, a difference of 0.9% has been observed between half-lives in metallic and insulating environments.[1] This relatively large effect is because beryllium is a small atom whose valence electrons are in 2s [4]s which have a large degree of penetration very close to the nucleus, and thus are subject to electron capture.

A number of experiments have found that decay rates of other modes of artificial and naturally-occurring radioisotopes are, to a high degree of precision, unaffected by external conditions such as temperature, pressure, the chemical environment and electric, magnetic or gravitational fields. Comparison of laboratory experiments over the last century, studies of the Oklo nuclear reactor, and astrophysical observations of the luminosity decays of distant supernovae (which occurred long ago so the light has taken a great deal of time to reach us), for example, strongly indicate that decay rates have been constant (at least to within the limitations of small experimental errors) as a function of time as well.

On the other hand, some recent results suggest the possibility that decay rates might have a weak dependence (0.5% or less) on environmental factors. It has been suggested that measurements of decay rates of[5]], [6] and [7] exhibit small seasonal variations (in order 0.1%), proposed to be related to either solar flare activity or distance from the sun.[2][3][4] However, such measurements are highly susceptible to systematic errors, and a subsequent paper [5] has found no evidence for such correlations in a half-dozen isotopes, and sets upper limits on the size of any such effects. However, research at [8] indicates that the rate of radioactive decay may not be truly constant, but slightly influenced by solar flares due to variations in [9] flux.[6]

Chemical and environmental influence

Highly ionized heavy ions (Bound-state beta decay)

Influence of the Sun

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