Observation of a μs isomer in In85 49134: Proton-neutron coupling "southeast" of Sn82 50132

Abstract

We report on the observation of a microsecond isomeric state in the single-proton-hole, three-neutron-particle nucleus In134. The nuclei of interest were produced by in-flight fission of a U238 beam at the Radioactive Isotope Beam Factory at RIKEN. The isomer depopulates through a γ ray of energy 56.7(1) keV and with a half-life of T1/2=3.5(4)μs. Based on the comparison with shell-model calculations, we interpret the isomer as the Iπ=5- member of the π0g9/2-1 - ν1f7/23 multiplet, decaying to the Iπ=7- ground state with a reduced-transition probability of B(E2;5-→7-)=0.53(6)W.u. Observation of this isomer, and lack of evidence in the current work for a Iπ=5- isomer decay in In132, provides a benchmark of the proton-neutron interaction in the region of the nuclear chart "southeast" of Sn132, where experimental information on excited states is sparse.