1p3/2 Proton-Hole State in 132Sn and the Shell Structure Along N=82.

A low-lying state in In82131, the one-proton hole nucleus with respect to double magic Sn132, was observed by its γ decay to the Iπ=1/2– β-emitting isomer. We identify the new state at an excitation energy of Ex=1353  keV, which was populated both in the β decay of 131Cd83 and after β-delayed neutron emission from 131Cd84, as the previously unknown πp3/2 single-hole state with respect to the 132Sn core. Exploiting this crucial new experimental information, shell-model calculations were performed to study the structure of experimentally inaccessible N=82 isotones below 132Sn. The results evidence a surprising absence of proton subshell closures along the chain of N=82 isotones. The consequences of this finding for the evolution of the N=82 shell gap along the r-process path are discussed. [ABSTRACT FROM AUTHOR]