Monopole-Driven Shell Evolution below the Doubly Magic Nucleus ~(132)Sn Explored with the Long-Lived Isomer in ~(126)Pd

摘要

A new isomer with a half-life of 23.0(8) ms has been identified at 2406 keVin ~(126)Pd and is proposed to have a spin and parity of 10~+ with a maximally aligned configuration comprising two neutron holes in the 1h_(11/2) orbit. In addition to an internal-decay branch through a hindered electric octupole transition, β decay from the long-lived isomer was observed to populate excited states at high spins in ~(126)Ag. The smaller energy difference between the 10~+ and 7~- isomers in ~(126)Pd than in the heavier N = SO isotones can be interpreted as being ascribed to the monopole shift of the 1h_(11/2) neutron orbit. The effects of the monopole interaction on the evolution of single-neutron energies below ~(132)Sn are discussed in terms of the central and tensor forces.