Isomer Decay Spectroscopy of Neutron-Rich Nuclei beyond N=126 Shell Closure

The region south of the heaviest double magic nuclei ²⁰⁸Pb, acting as a gateway past N = 126 shell closure that strongly affects the synthesis of heaviest elements during the merger of neutron stars [1], suffers from a severe lack of experimental data, with the current level scheme of ²⁰⁴Pt being the last N = 126 isotope only four neutrons away removed from Z = 82. A new opportunity to study nuclear shell and shape evolution in neutron-rich nuclei relevant to the r-process nucleosynthesis emerged from the beta-decay spectroscopy in the vicinity of the N = 126 closed shell. This contribution will focus on the preliminary results of isomeric states in the “southeast” of doubly-magic nucleus ²⁰⁸Pb identified in an experiment carried out in the “BRIKEN” decay-spectroscopy campaign at the RIBF facility, RIKEN [2]. The selected level schemes will be interpreted in terms of the shell model calculations. Future perspectives of contentiously exploring seniority schemes and shape evolution in this region will also be discussed.