Abstract
Recent developments of the projected shell model (PSM) are summarized. Firstly, by using the Pfaffian algorithm, the multi-quasiparticle configuration space is expanded to include 6-quasiparticle states. The yrast band of 166 Hf at very high spins is studied as an example, where the observed third back-bending in the moment of inertia is well reproduced and explained. Secondly, an angular-momentum projected generate coordinate method is developed based on PSM. The evolution of the low-lying states, including the second 0 + state, of the soft Gd, Dy, and Er isotopes to the well-deformed ones is calculated, and compared with experimental data.
Highlights
Nuclei are among the few quantum systems that can be discussed in terms of shape [1]
It is seen that deep minima are robustly developed at the deformation ε2 ≈ +0.25, no matter if the calculation is performed with or without angular momentum projection
The nucleon pairs in the orbitals with the highest angular momentum j, as for instance the neutron i13/2 shell in the rare earth region, feel a stronger Coriolis force, and break first [5]
Summary
Nuclei are among the few quantum systems that can be discussed in terms of shape [1]. A regular rotational band, with the band energies following the ∼ I(I +1) dependence expected from those of a classical rotor, has been observed experimentally [2] Physics for such regularly-deformed nuclei can be described by models that choose the known deformation to construct a deformed basis. The nucleon pairs in the orbitals with the highest angular momentum j, as for instance the neutron i13/2 shell in the rare earth region, feel a stronger Coriolis force, and break first [5] They contribute to the formation of a 2-qp state as the main con-. As the nucleus rotates, the minima change towards larger absolute values; namely, the nucleus becomes more and more deformed [20] For this kind of nuclei, one can not build a shell model basis with one deformation.
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