A multiparticle spin-trap isomeric state having a half-life of 179(4) ns and lying 2601 keV above the yrast ${10}^{+}$ state in ${}^{156}\mathrm{Lu}$ has been discovered. The ${}^{156}\mathrm{Lu}$ nuclei were produced by bombarding isotopically enriched ${}^{106}\mathrm{Cd}$ targets with beams of ${}^{58}\mathrm{Ni}$ 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 ${}^{156}\mathrm{Lu}$ indicates that the $[\pi h_{11/2}^{-1}\otimes \nu h_{9/2}]{10}^{+}$ state at the bottom of the yrast sequence is likely to be the $\alpha$-decaying isomeric state, with the $[\pi h_{11/2}^{-1}\otimes \nu f_{7/2}]9^{+}$ state lying 62 keV above it. The relative ordering of the lowest-lying $9^{+}$ and ${10}^{+}$ states is inverted in ${}^{156}\mathrm{Lu}$ compared with its odd-odd isotones.

• Received 13 June 2018

DOI:https://doi.org/10.1103/PhysRevC.98.024302