Reaction Rates for 146Sm Production in Supernovae
T. Rauscher, F.-K. Thielemann, H. Oberhummer;
Ap. J. Lett. 451 (1995) L37.
Abstract:
Correlations of the $^{142}$Nd/$^{144}$Nd ratio with the Sm/Nd ratio in
some meteorites have been previously explained by the $\alpha$-decay of
long-lived $^{146}$Sm. In order to account for these observations, a
necessary production ratio for $^{146}$Sm/$^{144}$Sm in the $\gamma$-process
of 0.1--0.7 was deduced. The ratio
($^{148}$Gd($\gamma$,n)$^{147}$Gd)/($^{148}$Gd($\gamma$,$\alpha$)$^{144}$Sm),
which plays the dominant role in the production of $^{146}$Sm/$^{144}$Sm,
has been re-determined in the present paper by improved statistical model
calculations. Utilization of folding potentials for the $\alpha$-channel reduce
the ($\gamma$,$\alpha$) rate by a factor of 3, which would enhance the
production ratios, previously predicted at the lower limit of the allowed
range 0.1--0.7. However, additional improvements in the treatment of nuclear
level densities also reduce the ($\gamma$,n) rate by a factor of 0.4. Thus,
in total the new cross section calculations result, at best, only in a modestly
enhanced production ratio of $^{146}$Sm/$^{144}$Sm.

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