Multiparticle configurations of excited states in Lu 155

Abstract

Excited states in the neutron-deficient N=84 nuclide Lu155 have been populated by using the Pd102(Ni58,αp) reaction. The Lu155 nuclei were separated by using the gas-filled recoil ion transport unit (RITU) separator and implanted into the Si detectors of the gamma recoil electron alpha tagging (GREAT) spectrometer. Prompt γ-ray emissions measured at the target position using the JUROGAM Ge detector array were assigned to Lu155 through correlations with α decays measured in GREAT. Structures feeding the (11/2-) and (25/2-)α-decaying states have been revised and extended. Shell-model calculations have been performed and are found to reproduce the excitation energies of several of the low-lying states observed to within an average of 71 keV. In particular, the seniority inversion of the 25/2- and 27/2- states is reproduced.