🚀 go-pugleaf

Jeppe Stig Nielsen wrote:
> 
> Heavy nuclei are usually surrounded by a large number of orbital electrons.
> Some unstable, proton-rich nuclei primarily decay by capturing an orbital
> electron from the 1st shell (the K shell), like
> 
>    p + e  ->  n + neutrino
> 
> My question is this: If you strip away *all* electrons from such a nucleus,
> making K-capture impossible, how much may the life-time of the nucleus be
> increased (in percents)?
> 
> Are there table values for the life-times of these "isolated" nuclei? The
> usual tables are valid for nuclei in electrically neutral atoms only.

The half-lives increase.  The famous case for altering electron
capture half-life is a tantalum isotope compared in the metal and as
tantalum pentafluoride - several percent difference.  Look at Ta-175
and Ta-176; Ta-177 and Ta-179.

The naked nucleus case is doable in principle - strip the atom then
hold it in an ion cyclotron resonance spectometer.  The problem is
obvious: the first electron to be captured is going right in.  It's a
labor or Hercules to get a vacuum clean enough to do the job. 
Electron nuclei often also decay by alpha or position emission
channels, which adds noise.  You need an isotope which sticks around
long enough to be manipulated, but doesn't require long observaiton
times for decay kinetics.  It's a tough experiment.

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