1p_3/2 proton-hole state in ¹³²Sn and the shell structure along N = 82

A low-lying state in ¹³¹In₈₂, the one-proton hole nucleus with respect to double magic ¹³²Sn, was observed by its γ decay to the I^π 1/2^- β-emitting isomer. We identify the new state at an excitation energy of E_λ= 1353 keV, which was populated both in the β decay of ¹³¹Cd₈₃ and after β-delayed neutron emission from ¹³²Cd₈₄, as the previously unknown πp_3/2 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. (authors)