Speaker
Description
Neutron-capture cross sections are essential nuclear physics inputs for modeling the s-process nucleosynthesis, which is responsible for producing approximately half of the elements heavier than iron in the Universe. The isotope {}^{191}_{77}\mathrm{Ir} plays an important role in the s-process because neutron capture on $^{191}\mathrm{Ir}$ produces $^{192}\mathrm{Ir}$, a branching-point nucleus that influences the nucleosynthesis flow in the iridium-platinum-osmium mass region. However, existing experimental measurements and evaluated nuclear data libraries for the {}^{191}\mathrm{Ir}(n,\gamma){}^{192}\mathrm{Ir} reaction show significant discrepancies, leading to uncertainties in astrophysical reaction rates and abundance predictions. In this work, the neutron-capture cross section of the {}^{191}\mathrm{Ir}(n,\gamma){}^{192}\mathrm{Ir} reaction was investigated using theoretical calculations. Calculations were performed using the TALYS-2.2 nuclear reaction code with six different nuclear level density models. The calculated cross sections were validated against experimental data available in the EXFOR database and compared with the latest version of the evaluated nuclear data libraries ENDF/B-VIII.1, JEFF-4.0, JENDL-5, TENDL-2025, and BROND-3.1. The results indicate that the microscopic Skyrme-Hartree-Fock-Bogoliubov (SHFB) and Gogny-Hartree-Fock-Bogoliubov (GHFB) level density models provide the best agreement with experimental observations. MACSs and stellar reaction rates were determined for the astrophysically relevant temperature range of $kT = 5$--$100\,\mathrm{keV}$. The derived reaction rates are systematically lower than the recommended KADoNiS 0.3 values. Implementation of the new MACSs in the NETZ s-process network calculations shows an increase of approximately 5.2\% in the final abundance of 191Ir during He-shell flash conditions in thermally pulsing asymptotic giant branch (TP-AGB) stars. These results provide improved nuclear data for {}^{191}\mathrm{Ir} and contribute to a more reliable understanding of heavy-element nucleosynthesis in stellar environments.
| Category | Theory |
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