Decay of a 19^- isomeric state in ¹⁵⁶Lu

A multiparticle spin-trap isomeric state having a half-life of 179(4) ns and lying 2601 keV above the yrast 10⁺ state in ¹⁵⁶Lu has been discovered. The ¹⁵⁶Lu nuclei were produced by bombarding isotopically enriched ¹⁰⁶Cd targets with beams of ⁵⁸Ni ions, separated in flight using the gas-filled separator RITU and their decays were measured using the GREAT spectrometer. Analysis of the main decay path that populates yrast states observed previously suggests a spin-parity assignment of 19− for the isomeric state, which is consistent with isomeric states identified in the N = 85 isotones. Comparison with other decay paths in ¹⁵⁶Lu indicates that the [πh−111/2⊗νh_9/2]10⁺ state at the bottom of the yrast sequence is likely to be the α-decaying isomeric state, with the [πh−111/2⊗νf_7/2]9⁺ state lying 62 keV above it. The relative ordering of the lowest-lying 9⁺ and 10⁺ states is inverted in ¹⁵⁶Lu compared with its odd-odd isotones.