Abstract
Delayed gamma-ray spectroscopy was performed for evaporation residues produced in the 58Ni + 96Ru reaction. A new isomer in 150 70Yb (Z = 70, N = 80) with a half-life of 0.62(5) mu s was identified at an excitation energy of 2872(2) keV. Its spin-parity is assigned as (10+) and a decay scheme is proposed based on a strong analogy with that of the isotonic 148 68Er. Previously, the 10+ isomers were observed in the N = 80 even-Z isotones from the neutron-rich 12646Pd to the neutron-deficient 14868Er. For the first time, by combining experimental data and comprehensive large-scale shell-model calculations, we clearly identify the configurations of these isomers and demonstrate that they all exhibit seniority structures. These findings firmly establish a configuration change in the 10+ isomeric chain, from a pair of maximally aligned 1h11/2 neutrons (holes) to a pair of maximally aligned 1h11/2 protons around the Z = 64 subshell closure. This transition serves as a unique isomeric relay underpinning the persistence of the isomeric chain.