Isomers with exceptionally long half-lives in ^205,206Bi

Nuclear isomers are metastable states which are realized due to the hindrance in the de-excitation of that nuclear level. This hindrance can result from either large spin, shape or angular momentum projection change between neighbouring levels. Quantum mechanically, a substantial difference in the associated wave functions of nearby levels can lead to isomerism. This usually brings in up to orders of magnitude of difference between the transition rates associated with the decay of such levels when compared with non-isomeric transitions. The study of such isomeric nuclear levels provides crucial insights towards the understanding of nuclear phenomena and the interactions leading to the specific structure of that nucleus and the region in general. Thus, isomeric properties also play an important role in improving effective interactions for shell-model calculations of near-spherical nuclei. The present work was motivated by the fact that isotopes near the ²⁰⁸Pb region exhibit the presence of isomeric levels with half-lives ranging from nanoseconds up to the hundreds of microseconds time range at different excitation energies