Gao Zao-Chun

Reflection asymmetric shell model for the description of octupole rotational bands

The reflection asymmetric shell model has been formulated to describe the high spin states of octupole-deformed nuclei. The long-range separable forces of quadrupole, octupole and hexadecapole, as well as monopole and quadrupole pairing, are included in the Hamiltonian. The bases, on which the Hamiltonian is diagonalized, are the eigenstates of angular momentum and parity obtained by projecting the octupole-deformed multi-quasiparticle states onto good angular momentum and good parity. The general features of rotational octupole bands in even-even nuclei can be reproduced by the model and the calculated result is in good agreement with experiment.

Measurements of g-Factor of Rotational Levels in 83Y

The g-factors of the positive parity rotational levels up to spin I = 41/2+ in 83Y have been measured by a transient-magnetic-field ion implantation perturbed angular distribution method. The experimentally measured g-factors show the g9/2 proton alignment followed by the g9/2 neutron alignment. The measured g-factors are in good agreement with the results calculated by an empirical formula based on the cranking shell model.

Garvey-Kelson Mass Relations and n-p Interaction

Two Garvey-Kelson mass relations are found to be directly related to the n-p interaction. In the case of the same nuclear core, the neutron-proton interaction energy between two neutrons and one proton epsilon (2n-1p) is experimentally found to be close to that between one neutron and two Protons epsilon (1n-2p), which is equivalent to the first Garvey-Kelson mass relation. The sum of epsilon (2n-1p) and epsilon (1n-2p) is close to the n-p interaction energy between two neutrons and two protons epsilon (2n-2p), which leads to the second Garvey Kelson mass relation. An explanation of these two n-p interaction relations is presented. It is shown that both of these mass relations hold more accurately when the core is an even-even core.

Rotational State g-Factors in 84Zr

The g-factors of the rotational states along the positive parity yrast band in even-even nuclei 84Zr were measured up to a spin I = 16+ by a transient magnetic field-ion implanted perturbed angular distribution method and calculated by a cranking shell model. A peak structure of the g-factors has been observed for the first time. The measured g-factors confirm the mixed configuration of proton and neutron alignments.

Triaxial rotation in atomic nuclei

The Projected Shell Model has been developed to include the spontaneously broken axial symmetry so that the rapidly rotating triaxial nuclei can be described microscopically. The theory provides an useful tool to gain an insight into how a triaxial nucleus rotates, a fundamental question in nuclear structure. We shall address some current interests that are strongly associated with the triaxial rotation. A feasible method to explore the problem has been suggested.

Reflection-Asymmetric Shell Model Description of the Neutron-Rich 142,145Ba Nuclei

The reflection asymmetric shell model has been applied to describe the octupole deformed bands in neutron-rich even-even 142Ba and odd-N 145Ba nuclei. The alternating parity bands of 142Ba and the simplex s = −i bands of 145Ba are calculated and compared with the available experimental data. The calculated results are in good agreement with the experimental data. The spin and parity assignments of ground-state of 145Ba are discussed. The results show that the present work is a useful attempt to further explore the nuclear reflection asymmetry in neutron rich region.

The structure of the spherical tensor forces in the USD and GXPF1A shell model Hamiltonians

The realistic shell model Hamiltonians, USD and GXPF1A, have been transformed from the particle-particle (normal) representation to the particle-hole representation (multipole-multipole) by using the known formulation in Ref. [1]. The obtained multipole-multipole terms were compared with the known spherical tensor forces, including the coupled ones. It is the first time the contributions of the coupled tensor forces to the shell model Hamiltonian have been investigated. It has been shown that some coupled-tensor forces, such as [r2Y2 ⊗ σ]1, also give important contributions to the shell model Hamiltonian.

g‐factor Measurement of High Spin States in 83Y by TMF‐IMPAD

The g‐factors of high spin states of the positive parity yrast rotational band up to spin I=41/2+ in 83Y have been measured by a transient‐magnetic‐field ion implantation perturbed angular distribution method. A positive peak structure of g‐factor vs spin has been observed, which provides an experimental evidence for the g9/2 proton alignment followed by the g9/2 neutron alignment.

Rotational Band Structures of Non-Axial Octupole Deformed Shapes

The rotational band structures associated with the intrinsic non-axial octupole deformed states, especially for the intrinsic ground state of the even-even nuclei, are analysed by using the reflection asymmetric shell model. These band structures are expected to be useful in identifying such exotic shapes from experiment. As an example, a possible triangular shape Of Sm-148 is suggested.

Theoretical Simulation for Identical Bands

The frequency of occurrence of identical bands is studied by analysing a large number of rotational bands calculated with the reflection asymmetric shell model, and the statistical properties of identical bands indicated in all the experimental observations are reproduced within the mean field approximation and beyond mean field treatment, such as angular momentum projection. The distributions of the calculated J(2), Eγ and the fractional change of J(2) are discussed.