Two-quasiparticle bands in A = 100 region of neutron-rich nuclei

In the present work triple, prompt γ-ray coincidence data following the spontaneous fission of 248Cm have been used to search for excited bands in neutron-rich nuclei based upon two-quasiparticle intrinsic structures. Such bands have been found in several even-even nuclei from 96Sr to 112Pd. Careful analysis of double-gated spectra has been performed in order to determine branching ratios within the bands. These branching ratios are then used to establish the magnetic properties of the intrinsic structure, permitting, in many cases, the determination of which Nilsson orbits (and whether they are neutron or proton states) are contributing to the excitation. The results of the investigation are presented, and the single-particle states involved in the two-quasiparticle excitations in some of the nuclei studied are identified. The lowest-lying two-quasiparticle states will be at an excitation energy of approximately 2 Δ above the even-even ground state. If these lowest-lying bands are systematically populated, then it would allow us to determine the single-particle orbits at the Fermi surface as the nuclear mass number and deformation varies. One interesting feature that arises from the present study is that the population mechanism in fission plays an important role in deciding what two-quasiparticle states are actually observed.