Multi-quasiparticle Rotational Bands Research Articles

Multi-quasiparticle rotational bands in neutron-rich erbium isotopes

Multi-quasiparticle states and rotational bands in neutron-rich erbium isotopes have been investigated by the configurationconstrained pairing-deformation-frequency self-consistent total-Routhian-surface (TRS) method with particle-number-conserved pairing. Specifically, the recently observed K fy = 4− bands in 168,170,172Er have been found to experience a configuration change in our calculation. Some other multi-quasiparticle states with uncertain configuration assignments have been reinvestigated by calculating their collective rotations. The configuration-constrained TRS calculation can reproduce experimental data consistently.

Electromagnetic transition rates in high-spin bands inNd136

Lifetimes have been measured for transitions in the two multiquasiparticle rotational bands in the nucleus $^{136}\mathrm{Nd}$. The extracted transition probabilities are compared with results of tilted-axis cranking and random-phase approximation calculations. The bands are identified as being built on two distinct quasiparticle configurations, with very different associated transition rates. These findings are contrary to an earlier suggestion that the bands form a chiral-band pair in this even-even nucleus.

Shell-model description of heavier 1f7/2 nuclei

Natural parity states of odd-A and even–even nuclei in the middle and in the second half of the 1f7/2 shell are described by shell-model calculations in the full pf configuration space. Multi-quasiparticle rotational bands and, in some cases, band crossings have been revealed. The ground-state bands experience a change from collective to non-collective regime, approaching the termination in the 1fn7/2 space. Evidence of the vibrational γ-band is discussed in 52Fe.

Shell-model description ofN≃Z1f7/2nuclei

The available spectroscopic data for nuclei middle and second half of the $1{f}_{7/2}$ shell are well reproduced by shell-model calculations. For natural parity states of several odd-A nuclei, a comparison of shell-model calculations in the full pf configuration space with the Nilsson diagram and particle-rotor predictions shows that prolate strong coupling applies at low excitation energy. Multiquasiparticle rotational bands and, in some cases, band crossings have been revealed. Coriolis decoupling effects are observed only in nuclei at the beginning of the shell. The ground state bands experience a change from a collective to a noncollective regime, approaching the termination in the $1{f}_{7/2}^{n}$ space. Similar features are observed in the even-even $N\phantom{\rule{0.3em}{0ex}}=\phantom{\rule{0.3em}{0ex}}Z$ nuclei $^{48}\mathrm{Cr}$ and $^{52}\mathrm{Fe}$ and $N=Z+2$ nuclei $^{46}\mathrm{Ti}$ and $^{50}\mathrm{Cr}$. Evidence of the vibrational \ensuremath{\gamma} band is discussed in the $N=Z$ nuclei. A brief review is also presented for unnatural parity levels.

Nonadditivity in nuclear moments of inertia and interference between blocking effects

The experimentally observed obvious nonadditivity in the nuclear moment of inertia and angular momentum alignment of multiquasiparticle rotational bands, both in normally deformed and superdeformed nuclei, presents a serious challenge to the traditional BCS treatment for nuclear pairing. It is shown that the systematically observed nonadditivity mainly comes from the destructive interference between blocking effects, and can be satisfactorily accounted for by the particle-number conserving method, in which the blocking effects are treated consistently and exactly.