Shell-model study on spectroscopic properties in the region “south” of Pb208

Background: The properties of nuclei located in the region ``south'' of $^{208}\mathrm{Pb}$ are important for understanding the $r$-process nucleosynthesis. While some isomeric states and their spectroscopic properties have been investigated experimentally in neutron-rich Pb, Tl, and Hg isotopes recently, a large portion of the area still remains unreachable.Purpose: We aim to study the properties of nuclei in the region south of $^{208}\mathrm{Pb}$, including the binding and excitation energies and electromagnetic properties, in order to predict unknown properties of these nuclei, such as isomerism, utilizing a theoretical model which describes the experimentally known properties precisely. We also address whether the $N=126$ shell closure is robust or not when the proton number decreases from $^{208}\mathrm{Pb}$.Methods: We performed large-scale shell-model calculations with a new Hamiltonian suggested in the present work. The model space is taken as the 5 proton orbits within $50更多