Evolution of nuclear structure through isomerism in Fr216

Abstract

Three new isomers have been identified in the transitional odd-odd $^{216}\mathrm{Fr}$ 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 $[{J}^{\ensuremath{\pi}}>({18}^{+})]$ 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.