Shen Cai-Wan

Calculation of triaxial superdeformation in Hf-174

A two-dimensional Total Routhian Surface (TRS) calculation with the fixed hexadecapole deformation ε4 = 0.03 was carried out for several configurations of 174Hf. Results indicate that the shell corrections have an important contribution to the formation of triaxial superdeformation in 174Hf and some possible configuration assignments are made to the 4 TSD bands experimentally found in 174Hf.

A tentative method for assigning the configuration of a triaxial nuclei in TRS

A tentative method based on the principle of minimum energy is put forward for assigning the reasonable configuration of a triaxial nucleus in TRS. This method is proved by the TSD of 167Lu nucleus that has been calculated previously by TRS.

Formation Mechanism of Triaxial Superdeformed Nucleus 160Yb

By using Total Routhian Surface (TRS) method the deformation of the nucleus 160Yb is studied. The result shows that the triaxial superdeformed state exists with deformation parameters 2 = 0.38 and γ = 21°, where proton shell correction energy plays a key role, and the sum of two quasi-proton particle energies gives an additional driving effect. The rotational energy also has an additional role in the formation of triaxial superdeformed.

Possible existence of triaxial superdeformation in 172,174,176W

Two-dimensional total routhian surface (TRS) calculations are carried out to determine the triaxial superdeformation (TSD) of the even-even nucleus W, and the result indicates that TSD state exists with deformation parameters 2 = 0.42 and ? = 34.7?. In the same way, the total routhian surfaces for the nuclei W are also calculated. It shows that the neutron shell correction energy plays a key role in the formation of TSD nuclei 172,174,176W, while the high j intruder orbitals and rotational energy are also crucial in the formation mechanism.

Total routhian surface calculations on Hf isotopes

The two-dimensional total routhian surface calculations have been carried out to study the triaxial superdeformed structure of a neutron-rich nucleus Hf-173 firstly. In particular the effects of the rotational frequency omega and pairing-energy gap parameter Delta are discussed in detail in the course of shaping its triaxial superdeformation; additionally the neutron-shell correction energy is analyzed with emphasis in the confirmed triaxial superdeformed nucleus Hf-173. Finally, more systematical results have been investigated for some confirmed superdeformed nuclei experimentally and a few predicted triaxial superdeformed nuclei theoretically with quadropole deformation epsilon(2) approximate to 0.4 and triaxial deformation gamma approximate to 20 degrees or 30 degrees in the Z = 72 region.

Isovector scalar field effects in asymmetric nuclear matter

Density-dependent parametrization models of the nucleon-meson coupling constants, including the isovector scalar delta-field, are applied to asymmetric nuclear matter. The nuclear equation of state (EOS) and the neutron star properties are studied in a relativistic Lagrangian density, using the relativistic mean field (RMF) hadron theory. It is known that the delta-fleld in the constant coupling scheme leads to a larger repulsion in dense neutron-rich matter and to a definite splitting of proton and neutron effective masses, finally influences the stability of the neutron stars. We use density-dependent models of the nucleon-meson couplings to study the properties of neutron star matter and to reexamine the delta-held effects in asymmetric nuclear matter. Our calculation shows that the stability conditions of the neutron star matter can be improved in presence of the delta-meson in the density-dependent models of the coupling constants. The EOS of nuclear matter strongly depends on the density dependence of the interactions.

Study of Triaxial Superdeformation in 162Lu

The triaxially superdeformed states in 162Lu are investigated using the three-dimensional total routhian surface calculation, and the deformation parameters and the likely configuration are given. The shell and pairing correction energies are considered respectively, and the formation mechanism of triaxial superdeformation is investigated.

Triaxial superdeformed band and its formation mechanism in odd-odd nucleus Lu-168

Three-dimensional total Routhian surface calculations are carried out to determine the triaxial superdeformation of odd-odd nucleus Lu-168. One of the new four rotational bands observed in the experiment is identified as a triaxial superdeformed band, in which the neutron shell correction energy plays a key role and the deformation-driving effect of high j intruder orbital plays an additional role in the formation of triaxial superdeformation shape. Its deformation parameters (epsilon(2), epsilon(4), gamma) are derived from the analysis, which can reproduce the experimental assignment.

Spin—Polarized States of Nuclear Matter

The equations of state of spin-polarized nuclear matter and pure neutron matter are studied in the framework of the Brueckner–Hartree–Fock theory including a three-body force. The energy per nucleon EA(δ) calculated in the full range of spin polarization for symmetric nuclear matter and pure neutron matter fulfills a parabolic law. In both the cases the spin-symmetry energy is calculated as a function of the baryonic density along with the related quantities such as the magnetic susceptibility and the Landau parameter G0. The main effect of the three-body force is to strongly reduce the degenerate Fermi gas magnetic susceptibility even more than the value with only two-body force. The equation of state is monotonically increasing with the density for all spin-aligned configurations studied here so that no any signature is found for a spontaneous transition to a ferromagnetic state.

Prediction of Triaxial Superdeformation in the A ∼ 160, 80 Region

The discovery of the triaxial superdeformed bands provide a new opportunity to understand the axial symmetry breaking even in highly elongated nuclei. A total of 17 triaxial superdeformed nuclei in the mass A ~ 160 region and 11 in the mass A ~ 80 region are predicted by the three dimensional total routhian surface calculations. A possible way to identify the triaxiality of triaxial superdeformed nuclei is suggested.