Level structures in the odd-odd nucleus 154Pm

Critical examination of data from beta-decays of Nd-154, 2.68m Pm-154 and 1.73m Pm-154 is undertaken with a view to unravelling the Pm-154(61)93 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 Pm-154 ground state (gs) with J(pi) = 4(+) and 2qp configuration 4(+){p:5/2[532] circle times n:3/2[521]}. The 1.73m Pm-154 isomer is assigned J(pi) = 1(-) and 2qp configuration 1(-){p:5/2[413] circle times 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 beta-connected states.