Nucleosynthesis in the Cd-In-Sn region

The abundance contributions from the possible nucleosynthesis mechanisms to the rare isotopes ¹¹³In, ¹¹⁴Sn, and ¹¹⁵Sn are investigated. The level scheme of ¹¹³Cd was studied via the (n, n′γ) reaction up to 2.5 MeV excitation energy, searching for gateway levels that can provide for thermal equilibration of ground state and isomer under stellar conditions. The experiment confirmed the lowest gateway level at 522 keV, which provides for thermal equilibrium at temperatures above 10⁸ K, resulting in the destruction of the isomer in all plausible s-process scenarios. Accordingly, the importance of the branching at ¹¹³Cd is strongly reduced, allowing only for small s-process yields of ¹¹³In, ¹¹⁴Sn, and ¹¹⁵Sn of <0.3%, <0.5%, and <8%, regardless of the model used. The r-contributions to these isotopes were found to range between 0% and 40%, depending on the post-r-process conditions, and are also not sufficient to account for the observed abundances. For ¹¹⁴Sn the remaining abundance contribution can be accounted for by recent p-process calculations, but a different production mechanism seems to be required for ¹¹³In and ¹¹⁵Sn.