Level structures in the odd–odd nucleus 154Pm

Abstract

Critical examination of data from β-decays of 154Nd, 2.68m 154Pm and 1.73m 154Pm is undertaken with a view to unravelling the 15461Pm93 level structures. Guidance is sought from evaluation of two-quasi-particle (2qp) bandhead energies based on the mapping of the physically admissible configuration space with inputs from observed 1qp energies in the core odd-mass isotope and isotone, and the experimental 2qp level energies in the neighbouring odd–odd nuclei. Our analysis leads us to conclude that the 2.68m isomer is the 154Pm ground state (gs) with J π = 4+ and 2qp configuration 4+{p:5/2[532] ⊗ n:3/2[521]}. The 1.73m 154Pm isomer is assigned J π = 1− and 2qp configuration 1−{p:5/2[413] ⊗ n:3/2[521]}; our calculations place it (30 ± 10) keV above the 4+ gs. Structures of several other 154Pm levels are also discussed. These investigations again support our earlier stated proposition that the log ft values, by themselves, cannot yield the relative parity of β-connected states.