Reaction rates for 146sm production in supernovae

Correlations of the¹⁴²Nd/¹⁴⁴Nd ratio with the Sm/Nd ratio in some meteorites have been previously explained by the a-decay of long-lived 146Sm. In order to account for these observations, a necessary production ratio for 146Sm/144Sm in the y-process of 0.1-0.7 was deduced. The ratio [148Gd(ϓ, n)147Gd]/[148Gd(ϓ, α)144Sm], which plays the dominant role in the production of 146Sm/144Sm, has been redetermined in the present Letter by improved statistical model calculations. Utilization of folding potentials for the a-channel reduce the (y, a) 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 (y, n) rate by a factor of 0.4. Thus, in total the new cross section calculations result, at best, in only a modestly enhanced production ratio of 146Sm/144Sm.