What is the validity of half lives being constant in all radioactive isotopes?

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Discussion Overview

The discussion revolves around the validity of the constancy of half-lives in radioactive isotopes, particularly in light of claims that certain isotopes may exhibit variable half-lives under specific conditions. The scope includes theoretical considerations and implications for dating methods.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant cites a paper suggesting that the half-lives of certain radioactive isotopes can change, potentially by around 1%, and questions whether this applies to all isotopes or just specific ones.
  • Another participant notes that isotopes decaying by electron capture can have their half-lives altered by changes in electronic configuration, including complete ionization.
  • A further contribution mentions that fully ionized Re-187 is stable against beta decay due to shifts in beta energy caused by electron configuration changes.
  • One participant expresses confusion about the nature of radioactivity, suggesting it is based on nuclear instability and probability, and questions the reliability of certain isotopes for dating purposes.
  • In response, another participant argues that environmental changes affecting half-lives are typically minuscule and do not significantly impact methods like K-Ar dating.

Areas of Agreement / Disagreement

Participants express differing views on the constancy of half-lives, with some suggesting variability under certain conditions while others maintain that such changes are negligible for practical applications. The discussion remains unresolved regarding the general applicability of these claims to all radioactive isotopes.

Contextual Notes

Limitations include the dependence on specific conditions affecting half-lives, such as electronic configuration, and the unresolved nature of how broadly these findings apply across different isotopes.

hunt_mat
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Hi,

I has talking to someone aboutthe half lives of certain radioactive isotopes not be constant. He cited this paper:
Chih-An Huh, “Dependence of the Decay Rate of 7Be on Chemical Forms,” Earth and Planetary Science Letters 171(1999):325-328

And it seems that they can change, and quite considerably, to within around 1% or so. So my question is, would this be valid for all radioactive isotopes or just certain ones?

Mat
 
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Isotopes that decay by electron capture can have their half-lives changed by modifying the electronic configuration. In the extreme case, if you fully ionize a nucleus that decays by capturing an electron, it won't be able to decay.
 
To add, Re-187 is unstable against beta decay. Fully ionized Re-187 is stable: the electrons shift the beta energy by about 20 eV, but since the energy is very low (3 eV or so), it moves it from above threshold to below threshold.
 
Interesting. I thought that radioactivity was caused by instability of the nucleus and therefore was based upon probability for the decay.

So if some elements decay via electron capture they're probably not a good one to date things with?

Thanks for the information by the way.
 
The environmental changes are normally miniscule, so it doesn't matter. Electron capture works just fine in K-Ar dating.
 

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