NetNews Usenet Archive 1992 #18/NN_1992_18.iso/spool/sci/physics/fusion/2028

Internet Message Format | 1992-08-14 | 3.7 KB

Path: sparky!uunet!cs.utexas.edu!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!ames!pacbell.com!tandem!zorch!fusion
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Newsgroups: sci.physics.fusion
Subject: Nuclear Facts and Fancies
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Date: 14 Aug 92 23:13:55 GMT
Sender: [e-mail] (Scott Hazen Mueller)
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There have been in recent days a number of questions about nuclear physics
that have been left hanging or incorrectly answered.  Let me take a
shot at a few of them.

1) Nuclear shell model.  To clearify some of the most basic questions
on this forum you need to know only the first few shells.  They go as
follows: 1s1/2, 1p3/2, 1p1/2 and then the sd shell which includes
2s1/2, 1d5/2, 1d3/2.  To read this the first integer is the principle
quantum number, s indicates orbital angular momentum 0, p for 1, d for 2.
The fraction following the letter gives the total angular momentum
resulting from a combination of the orbital part and the spin which is
always 1/2.  In each orbit you can put up to 2j + 1 protons and 2j + 1
neutrons to completely fill a shell.  4He fills the first shell and that
makes a darn tight package.  Putting a 5th nucleon into next shell
or moving a nucleon up from the s shell takes lots of energy, and in
neither case can you form a bound system.  12C fills the 1p3/2 and
16O fills the 1p1/2.  If someone tries to sell you stock in a company
that is going to replace the shell model by a cluster model, demand
that they show their wares!

2)Gamma cross sections.  Robert Eachus seems a bit confused on this
question.  The first generalization is that a cross section is a
cross section and it is independent of the matrix in which the
nucleous is located.  That is true for nuclear processes unless some
very specific special conditions are satisfied, and MeV photons on
deuterons in a Pd lattice don't meet the conditions required for
coherent scattering.

3)Lattice vibration energies and nuclear reactions.  Thermal
energies at room temperature are in the electron volt energy range.
It takes several 10s of kiloelectron volts before much happens
by way of nuclear reactions.

4)Virtual neutrons.  The distances over which virtual particles can
roam decrease with increasing mass so when two nuclei exchange
their virtue, its photons first and pions next.  By the time neutrons
get involved its too late to coverup what has been going on.  One
of the nuclei will already have made an ash of itself.

5)Corporate Clusters.  Throughout the cold fusion era there has been
a tendency to use the words "nuclear model" and/or "theory" in a
very loose manner.  A few scribbles on the back of an envelope do
not constitute a proper theory of nuclear physics any more than
the plastic parts you can buy at the dime store will allow you to
construct a "model" of the space shuttle.  The recent press release
concerning the formation of a corporation to manufacture nuclear
models was loaded with lots of hype and extremely short on hard facts.
I am glad to see Warren Buck's disclaimer as to his connection to
this outfit.  Whether this is a legit business enterprise is not
for me to say, but I will say they haven't produced a legitimate
nuclear cluster model until they have shown a real calculation
which fits some real experimental data.  For the record Linus
Pauling's efforts in this area weren't so great either.  Having
won Nobel Prizes doesn't make one the universal genius.  And
having discovered an obscure isotope 40 years ago does not make
one a nuclear theorist.  Have any of these people associated
with this new CSC done any nuclear physics lately?

Dick Blue
NSCL @ MSU