Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] question on radioactivity of Tc and Pm



I don't really understand the question. I think it was Gell-Mann who said, "In the kingdom of the ants, all that is not forbidden is mandatory." Similarly for nuclear decays. So a better question is,
given a decay that is energetically possible, what selection rule forbids the decay?
Among nuclides with the same A values, we generally find beta decays where they are energetically allowed (including K-capture). Where the energetics permit alpha-decay, proton emission, or neutron emission, this generally happens. The neutron is, of course, unstable., the binding energy of the deuteron is sufficient to keep it from coming apart. There are theories that predict finite lifetime for the proton, and there is a cottagte industry that has spent about 3 decades setting lower limits on the lifetime (by beta-decay, violating baryon conservation) So which stable nuclide is bothering you, and what energetically allowable decay are you not understanding?
Regards,
Jack



On Mon, 5 Mar 2007, Eric Scerri wrote:


Thanks for the responses on my question but perhaps I could say a
little more by way of explanation.

Although I am sure that I will find that the isotopes of Tc have low
binding energy and that the odd/odd ratios etc. do not favor
stability of Tc isotopes I dont think this will explain why Tc sticks
out 'like a sore thumb' as the only element with atomic number less
than say 60 that behaves in this way. And its atomic number is not
even close to 60.

I suppose I am looking for a more qualitative or perhaps a causal
explanation rather than merely confirming what is already known by
substituting values into equations.

Or am I merely a poor deluded chemist wanting to see matters in terms
of elements characterized by Z values rather than treating isotopes
as the basic units?
Incidentally there is a whole story to tell on this point, some of
which I recount in the book which is mainly an examination of the
extent to which physics does or does not explain the periodic table.

regards,
eric scerri

------------------------------------------------------------------------
--------------
The Periodic Table: Its Story and Its Significance, by Eric Scerri,
Oxford University Press, 2006.

"An absolutely gorgeous book. I put it on my bedside table
and then stayed up half the night reading it - it is immensely
readable."
---Oliver Sacks, author of The Man Who Mistook his Wife
for a Hat, Awakenings etc.
------------------------------------------------------------------------
---------------------------------

Dr. Eric Scerri
Department of Chemistry & Biochemistry,
Charles Young Drive,
Los Angeles,
CA 90095-1569.

310 206 7443
fax: 310 206 2061

UCLA faculty web page: http://www.chem.ucla.edu/dept/Faculty/scerri/

Editor of Foundations of Chemistry,
http://www.springer.com/sgw/cda/frontpage/0,11855,4-40399-70-35545882-
detailsPage%253Djournal%257CmostViewedArticles%257CmostViewedArticles,
00.html

International Society for the Philosophy of Chemistry,
http://ispc.sas.upenn.edu/



_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l


--
"Trust me. I have a lot of experience at this."
General Custer's unremembered message to his men,
just before leading them into the Little Big Horn Valley