Abstract:

Recently proposed microscopic shell-model version of the Bohr-Mottelson collective model, defined by the chain S_p(12, R) ⊃ SU (1, 1) ⊗ SO(6) ⊃ U (1) ⊗ SU_pn(3) ⊗ SO(2) ⊃ SO(3) of the proton-neutron symplectic model, is shortly considered. It is applied to the microscopic shell-model description of the low-lying (rigid-flow) quadrupole dynamics in the lowest ground, γ, and β bands (or quasibands) for each of the three typical nuclear structure cases: 1) strongly deformed, 2) transitional; and 3) weakly deformed nuclei. Finally, it is shown how the present proton-neutron shell-model approach can be slightly modiffied in order to account for the irrotational- flow quadrupole dynamics of Bohr-Mottelson type observed in some nuclei.