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5u«
This means that the In^^^ in natuire cannot have been subject to a higher
temperature then about 0.3 Mev a k'V
for more then a few days, or else a larger
iwoportion of the nuclei of mass ll5 "would be present in the form of Sn ^o
By comparing this result with available data on excited states one finds that it
is not possible to account for "Wie abundance of the shielded nuclear species
by assuming beta decay from thermally excited levels hi^er than the ground state
of the intermediate odd-odd isobar-
According to the neutron capture theory,
shielded nuclei will f oi*m in the later stage of the neutaran build up when the
rate of the neutron capture processes becc^ies smaller than the average rate
of beta decay, so that the build up takes place in the stable nuclei regiono
They will then form from sufficiently long lived or stable odd A nuclei by
(?p^) and subsequi&nt beta decay of iisB odd-odd nucleic
These abundances,
however, cannot recdily be expected to follow the pattern required hy the sua
rules-
Light isotopes in the higher mass region
The neutron capture theory dcBS not account for the existence of the
t3rpe of shielded nuclei that have a lower binding energy than their shielding
isobars and are on the p side of the energy valley. The abundance of these
species is in general about ten times sraallar than that of the energetically
favoured type of shielded nuclideso
Their abundance is not correlated with their
relative binding enex^ieso
One can inomediately see this from the fact that
in a number of elenents the abundance of th«i lightest isotope is higher than that
of the second lightesto
This is the ease for Mo, Hu, Cd, Sn, Xe, and BEO
In the case of Ce and Ry the lightest isotope is only slightly less abundant
than the second liglitesto
The lightest isotqpe, of course, always has a smaller