Nuclear isomers in 259Sg and 255Rf

The production and radioactive decay of (259)Sg and its daughter products were investigated using a-decay spectroscopy and spontaneous-fission measurements. The isotope was produced in the fusion-evaporation reaction Pb-206(Cr-54, 1n) (259)Sg. This work presents first results for isomeric states in the isotopes (259)Sg and (255)Rf. In addition new results for spontaneous-fission properties and branching ratios of both isotopes are discussed. The new decay-spectroscopy data allowed extending the single-particle systematics of isotones with 151 and 153 neutrons. A change of the ground-state configuration in N = 153 isotones from 1/2(+)[620] to 11/2(-)[725] was observed for the first time.