Ponente
Descripción
The nuclear structure and β-decay properties of neutron-rich nuclei near the N=126 shell closure are important for understanding nuclear interaction in heavy nuclei and astrophysical processes. Sensitivity studies of r-process nucleosynthesis have shown that uncertainties in the predicted abundance around the A~195 peak depend considerably on the accuracy of β-decay rates of neutron-rich nuclei, especially those with proton numbers between Z=60 and Z=70. These isotopes, however, remain experimentally inaccessible at present. Consequently, astrophysical models for r-process rely on extrapolations from nuclear theory. Here, the relative contribution of First-Forbidden (FF) β-decay has been considered important for the total decay rate. In contrast, recent shell-model calculations suggest a reduced role of FF decays as proton number decreases, introducing additional uncertainties in theoretical prediction of r-process nuclei.
To address this uncertainty, we propose measurements of the β-decay half-lives of 203Ir (Z=77) and 202Os (Z=76), along with nuclear-structure studies of their daughter nuclei (203Pt and 202Ir) at the RIKEN Radioactive Isotope Beam Factory (RIBF). Using a fragmentation reaction of a 345 MeV/u 208Pb beam, neutron-rich isotopes will be produced, separated, and identified by the BigRIPS separator. Subsequent β-γ spectroscopy will be performed using the high-resolution and efficient ERUICA-2 (Euroball RIKEN Cluster Array) experimental setup. ERUICA-2 setup is expected to allow measurement of β-decay half-lives and following γ-ray transitions, providing insight into the significance of FF decay in the 203Ir and 202Os.
