Decay of a 19− isomeric state in 156Lu

Abstract

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 Lu has been discovered. The 156 Lu nuclei were produced by bombarding isotopically enriched 106 Cd targets with beams of 58 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 Lu indicates that the [ π h − 1 11 / 2 ⊗ ν h 9 / 2 ] 10 + state at the bottom of the yrast sequence is likely to be the α -decaying isomeric state, with the [ π h − 1 11 / 2 ⊗ ν 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 Lu compared with its odd-odd isotones.