Evolution of nuclear structure through isomerism in Fr-216

Three new isomers have been identified in the transitional odd-odd Fr-216 nucleus. The properties of the (11(+)) isomer with T-1/2 = 9.6(14) ns are compared with those of the similar isomeric states in neighboring doubly-odd nuclei. The experimental results are compared with predictions of shell-model calculations and a fair agreement is observed between the experimental and calculated excitation energies of the (11(+)) isomeric state and the states to which it decays. The deviation between the measured and calculated reduced transition probabilities suggests contribution from effects other than the single-particle degrees of freedom in these states. Evidence of two high-spin [J(pi) > (18(+))] isomers above 2.2 MeV excitation energy with T-1/2 = 7.8(14) and 89(9) ns is also presented. These isomers at high excitation energies reflect a pronounced change in the structure above the previously established level scheme, where moderate quadrupole collectivity and octupole correlations were evident.