NUCLEOSYNTHESIS IN THE CD-IN-SN REGION

The abundance contributions from the possible nucleosynthesis mechanis ms to the rare isotopes In-113, Sn-114, and Sn-115 are investigated. T he level scheme of Cd-113 was studied via the (n, n'gamma) reaction up to 2.5 MeV excitation energy, searching for gateway levels that can p rovide for thermal equilibration of ground state and isomer under stel lar conditions. The experiment confirmed the lowest gateway level at 5 22 keV, which provides for thermal equilibrium at temperatures above 1 0(8) K, resulting in the destruction of the isomer in all plausible s- process scenarios. Accordingly, the importance of the branching at Cd- 113 is strongly reduced, allowing only for small s-process yields of I n-113, Sn-114, and Sn-115 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 ar e also not sufficient to account for the observed abundances. For Sn-1 14 the remaining abundance contribution can be accounted for by recent p-process calculations, but a different production mechanism seems to be required for In-113 and Sn-115.