Reflection Asymmetric Relativistic Mean Field Approach and Its Application to the Octupole Deformed Nucleus ^226Ra

A reflection asymmetric relativistic mean field （RAS-RMF） approach is developed by expanding the equations of motion for both the nucleons and the mesons on the eigenfunctions of the two-centre harmonic-oscillator potential. The efficiency and reliability of the RAS-RMF approach are demonstrated in its application to the well-known octupole deformed nucleus 226Ra and the available data, including the binding energy and the deformation parameters, are well reproduced.     

Phenomenological Scaling of Rapidity Dependence for Anisotropic Flows in 25 MeV/nucleon Ca＋Ca by Quantum Molecular Dynamics Model

Anisotropic flows （v1, v2, v3 and v4） of light fragments up to the mass number 4 as a function of rapidity are studied for 25 MeV/nucleon ^40Ca ＋ ^40Ca at large impact parameters by a quantum molecular dynamics model. A phenomenological scaling behaviour of rapidity dependent flow parameters vn （n = 1, 2, 3 and 4） is found as a function of mass number plus a constant term, which may arise from the interplay of collective and random motions. In addition, v4/v2^2 keeps to be almost independent of rapidity and remains a rough constant of 1/2 for all light fragments.     

Coupling Parameter in the Single-j Shell Model

We propose a modified formula which is used to determine the coupling parameter C in the Hamiltonian of the single-j shell. In comparison with the previously known formula, the new formula improves the agreement between the intruder single-j levels and the Nilsson ones. For studies of chiral bands within the particle rotor model, the new coupling parameter will considerably influence the energy splitting between the doublet bands.     

Ultrahigh Spin Structures in 157,158,159Er

Rotational structures at ultrahigh spin in ^157,158,159 Er have been investigated with the configuration-dependent cranked Nilsson-Strutinsky approach. Configurations of observed bands are assigned and the corresponding deformations are given theoretically. The calculations suggest that one of ultrahigh spin bands in ^158 Er is triaxial highly deformed and the other is normal-deformed, while both ultrahigh spin bands in ^157Er are suggested to be triaxial highly deformed. The possible ultrahigh spin bands in ^159Er are predicted to be triaxial highly deformed and have shape coexistence in the same configuration. The configurations with two neutron holes in the Nose = 4 orbitals and two neutron holes in the h11/2 orbitals in ^159Er are favoured for ultrahigh spin states but unfavoured for band termination, which is similar to ultrahigh spin bands in ^157,15SEr.     

Theoretical Study on Negative Parity States of^（191,193,195,197） Au in Particle Triaxial-Rotor Model

By taking the particle triaxial-rotor model with variable moment of inertia, we investigate the energy spectra, the deformation and the single particle configuration of the negative-parity states in nuclei^（191,193,194,197） Au systemically. The calculated energy spectra agree well with experimental data. The obtained results indicate that the negative-parity states in^（191,193,195,197）Au originate from the proton-hole h11/2 configuration coupled to a triaxial oblate Hg core. Meanwhile the main single particle configuration of the bands 1, 2 and 3 are identified to be [5h11/2 1/2） （α=-1/2）, [5h11/2 1/2） （α = 1/2） and 15h9/2 7/2）, respectively.     

Phase structure of a two-fluid bosonic system

The phase diagram of a two-fluid bosonic system is investigated. The proton-neutron interacting boson model (IBM-2) possesses a rich phase structure involving three control parameters and multiple order parameters. The surfaces of quantum phase transition between spherical, axially symmetric deformed, and triaxial phases are determined, and the evolution of classical equilibrium properties across these transitions is investigated. Spectroscopic observables are considered in relation to the phase diagram.     

Three-Dimensional Angular Momentum Projected Relativistic Point-Coupling Approach for Low-Lying Excited States in 24Mg

A tull three-dimensional angular momentum projection on top ot a triaxial relativistic mean-fieid calculation is implemented for the first time. The underlying Lagrangian is a point coupling model and pairing correlations are taken into account by a monopole force. This method is applied for the low-lying excited states in ^24Mg. Good agreement with the experimental data is found for the ground state properties. A minimum in the potential energy surface for the 22^＋ state, with β≈ 0.55,7 γ≈ 10^o, is used as the basis to investigate the rotational energy spectrum as well as the corresponding B（E2） transition probabilities as compared to the available data.     

Examining the Chiral Geometry in l04Rh and l06Rh

The criteria for chiral doublet bands based on one particle and one hole coupled to a triaxial rotor have been summarized. Two representative cases in A - 100 odd-odd nuclei, nearly degenerate △I = 1 doublet bands in 104Rh and 106Rh, are checked against these chiral criteria. It is shown that 106Rh possesses better chiral geometry than 104Rh, although the energy near degeneracy is achieved in 104Rh in comparison with the constant energy separation of doublet bands in 106Rh.     

Rotational Bands of Some Neutron Deficient Odd-A Pt Isotopes in Particle-Triaxial-Rotor Model

Theoretical calculations are performed for neutron deficient Pt isotopes ^177pt and ^175,173,171 Pt in the particletriaxial-rotor model with variable moment of inertia. The obtained energy spectra agree with experimental data quite well. The calculated results indicate that all these nuclei are in triaxial rotation with ^177pt; being in prolate and ^175,173,171pt in oblate. Several levels are predicted for the 13/2^＋ band in ^169pt.     

Deformed shell model for T = 0, 1 and 2 bands in <Superscript>52</Superscript>Fe and <Superscript>72</Superscript>Kr

Deformed configuration mixing shell model based on Hartree-Fock states with extension to include isospin projection (DSMT) for two- and four-particle configurations (generated by particle-hole excitations) is applied to study the structure of the low-lying T = 0, 1 and 2 bands (or levels) in the even-even N = Z nuclei ⁵²Fe and ⁷²Kr. The pf-shell KB3 interaction for ⁵²Fe and a modified Kuos interaction for ⁷²Kr are employed in the calculations. In this first application of DSMT with four-particle T projection, low-spin (J 10) members of the T = 0, 1 and 2 bands in ⁵²Fe are compared with experiment including the known E2 transition strengths. The agreement between DSMT and experiment is reasonably good. Similarly, the low-spin members of the observed (prolate) yrast band in ⁷²Kr are also well described by DSMT.     

Exploration of Pseudospin Symmetry in the Resonant States

Taking ^120Sn as an example, we discuss the pseudospin symmetry in the single proton resonant states by examining the energies, widths and the wavefunctions. The information of the single proton resonant states in spherical nuclei are extracted from an analytic continuation in the coupling constant method within the framework of the self-consistent relativistic mean field theory under the relativistic boundary condition. We find small energy splitting in a pair of pseudospin partners in the resonant states. The lower components of the Dirac wavefunctions of a pseudospin doublet agree well in the region where nuclear potential dominates. It is concluded that the pseudospin symmetry is also well conserved for the resonant states in realistic nuclei.     

Disentangling the Effects of Thickness of the Neutron Skin and Symmetry Potential in Nucleon Induced Reactions on Sn Isotopes

The effects of density dependence of symmetry energy and the thickness of the neutron skin in proton （neutron） induced reactions on Sn isotopes are investigated by means of the improved molecular dynamics model. The investigation shows that the target size dependence of the reaction cross sections for proton induced reactions on Sn isotopes is sensitive to the density dependence of the symmetry energy and less sensitive to the thickness of the neutron skin of the target nuclei, but that, for neutron induced reactions on Sn isotopes, it is less sensitive to the density dependence of the symmetry energy and sensitive to the thickness of the neutron skin of the target nucleus.     

Impact Parameter Dependence of the Double Neutron/Proton Ratio of Nucleon Emissions in Isotopic Reaction Systems

Within the transport model IBUU04, we investigate the double neutron/proton ratio of free nucleons taken from two reaction systems using two Sn isotopes at a beam energy of 50 MeV/nucleon and with impact parameters 2fm, 4fm and 8fm, respectively. It is found that the double neutron/proton ratio from peripheral collisions is more sensitive to the density dependence of the symmetry energy than those from mid-central and central collisions.     

Microscopic calculations for upper-fp,g<Subscript>9/2</Subscript> shell nuclei: Ge &; Se

Shell-model calculations for isotopes of Ge and Se are reported where valence nucleons beyond the N = 28 = Z core occupy levels of the normal parity upper-fp shell (f_5/2,p_3/2,p_1/2) and the unique parity g_9/2 intruder configuration. Results are given for realistic interactions of the Kuo-Brown-3 type with various model space truncations that key in on the number of nucleon pairs allowed to occupy the intruder level. Electromagnetic (E2 & M1) rates as well as decay probabilities are calculated, some of which are key in determining the structure of “waiting point” nuclei that regulate certain nucleo-astrosynthesis processes. The role of the intruder level, which is treated on an equal footing with the normal parity levels, is shown to be important for reproducing structural details. The levels of the upper-fp shell are handled within the framework of a normal ls-coupled basis as well as its pseudo-SU(3) counterpart, and respectively, the g_9/2 as a single level and as a member for the complete gds shell. The second of these two approaches, namely, the SU(3) picture, allows one to better probe the effect of deformation.     

Double neutron/proton ratio of nucleon emissions in isotopic reaction systems as a robust probe of nuclear symmetry energy

The double neutron/proton ratio of nucleon emissions taken from two reaction systems using four isotopes of the same element, namely, the neutron/proton ratio in the neutron-rich system over that in the more symmetric system, has the advantage of reducing systematically the influence of the Coulomb force and the normally poor efficiencies of detecting low energy neutrons. The double ratio thus suffers less systematic errors. Within the IBUU04 transport model the double neutron/proton ratio is shown to have about the same sensitivity to the density dependence of nuclear symmetry energy as the single neutron/proton ratio in the neutron-rich system involved. The double neutron/proton ratio is therefore more useful for further constraining the symmetry energy of neutron-rich matter.     

Finding a Probe for Extracting Information on the Momentum Dependent-Interaction in Heavy Ion Collisions

The effect of momentum-dependent interaction on the kinetic energy spectrum of the neutron-proton ratio （ （n/p）gas）b（ Ek ） for 64Zn ＋64Zn is studied. It is found that （ （n/p）gas）b（ Ek ） sensitively depends on the momentumdependent interaction and weakly on the in-medium nucleon-nucleon cross section and symmetry potential. Therefore （ （n/p）gas）b（ Ek ） is a possible probe for extracting information on the momentum-dependent interaction in heavy ion collisions.