Re: Bismuth radioactive??

From: Crown-Horned Snorkack (chornedsnorkack_at_hushmail.com)
Date: 12/04/04 

Date: 4 Dec 2004 02:23:23 -0800

Uncle Al <UncleAl0@hate.spam.net> wrote in message news:<419578E5.2E683B40@hate.spam.net>...
> JenLin2005 wrote:
> >
> > I think recently they proved Bismuth was radioactive with a half-life of
> > 1.9x10^19 years. This makes me think a lot of elements are radioactive with
> > super-long half-lives. Is this possible?
>
> The instability was calculated then searched out. There are several
> isotopes with supremely long half-lives. One doubts there are any
> unsuspected ones that can sneak under modern calculations.
>
> Protons don't decay, as evidenced by 50 kilotonnes of water in
> Super-Kamiokande observed for about five years.

Are there any comprehensive overviews of long-lived isotopes suspected
of undergoing radioactive decay and the experimental results?

One issue is alphas, as for bismuth. I gather that most detected alpha
radiation has energies of several MeV. Do any have smaller energies,
like a few hundreds or few tens of keV?

I have heard it alleged that tungsten is unstable like bismuth - in
that every single longlived isotope (there are five) eventually
undergoes alpha decay. Can anyone confirm this with experimental upper
bounds of half-life? Energy is worthless because it can be computed
from nuclear masses without actually observing the decay.

Single betas and electron captures. There is supposed to be a law
against neighbouring isobars being stable to beta decay and electron
capture. Can anyone quote an experimental upper bound on the half-life
of, say, V-50?

Double beta decay and double electron capture. There is a plenty of
neighbouring isobars. Just which of them are actually observed, with
upper bound on half-life, to undergo double-beta decay or double
electron capture?

Which nuclei are really stable? Of which elements?

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