Shell Effect of Superheavy Nuclei in Self-consistent Mean-Field Models

We analyze in detail the numerical results of superheavy nuclei in deformed relativistic mean-field model and deformed Skyrme-Hartree-Fock model. The common points and differences of both models are systematically compared and discussed. Their consequences on the stability of superheavy nuclei are explored and explained. The theoreticalresults are compared with new data of superheavy nuclei from GSI and from Dubna and reasonable agreement is reached.Nuclear shell effect in superheavy region is analyzed and discussed. The spherical shell effect disappears in some cases due to the appearance of deformation or superdeformation in the ground states of nuclei, where valence nucleons occupysignificantly the intruder levels of nuclei. It is shown for the first time that the significant occupation of vaJence nucleons on the intruder states plays an important role for the ground state properties of superheavy nuclei. Nuclei are stable in the deformed or superdeformed configurations. We further point out that one cannot obtain the octupole deformation of even-even nuclei in the present relativistic mean-field model with the σ,ω and ρ mesons because there is no parityviolating interaction and the conservation of parity of even-even nuclei is a basic assumption of the present relativistic mean-field model.     

Shell Effect of Superheavy Nuclei in Self-consistent Mean-Field Models

We analyze in detail the numerical results of superheavy nuclei in deformed relativistic mean-field model and deformed Skyrme-Hartree-Fock model. The common points and differences of both models are systematically compared and discussed. Their consequences on the stability of superheavy nuclei are explored and explained. The theoretical results are compared with new data of superheavy nuclei from GSI and from Dubna and reasonable agreement is reached. Nuclear shell effect in superheavy region is analyzed and discussed. The spherical shell effect disappears in some cases due to the appearance of deformation or superdeformation in the ground states of nuclei, where valence nucleons occupy significantly the intruder levels of nuclei. It is shown for the first time that the significant occupation of valence nucleons on the intruder states plays an important role for the ground state properties of superheavy nuclei. Nuclei are stable in the deformed or superdeformed configurations. We further point out that one cannot obtain the octupole deformation of even-even nuclei in the present relativistic mean-field model with the σ, ω and ρ mesons because there is no parity violating interaction and the conservation of parity of even-even nuclei is a basic assumption of the present relativistic mean-field model.     

超重核的球形和变形壳结构

应用宏观 微观模型系统研究了超重核的形状和结构性质.其中,宏观能是由基于核子密度泛函的连续介质模型计算得到.计算结果很好地再现了超重核的结合能、α衰变能和寿命的实验数据.对单粒子能级的计算和分析表明超重核的壳结构是形变和同位旋相关的.位能曲面的计算结果显示,与其它区域的核相比,超重核的形状不易变化. The structure of superheavy nuclei has been studied by using the macroscopic-microscopic model. The macroscopic energy was calculated with the continuous medium model in which the energy is expressed as a functional of nucleon densities. The deformations and structures of superheavy nuclei were investigated systematically. Calculations reproduce well the available data of experimental α decay energies and half-lifes. The investigation of single-particle levels shows that the shell structure is deformed a...     

Ground State Properties of Superheavy Nuclei in Macroscopic-Microscopic Model

The ground state properties of superheavy nuclei are systematically calculated by the macroscopic- microscopic （MM） model with the Nilsson potential. The calculations well produced the ground state binding energies, α-decay energies, and half lives of superheavy nuclei. The calculated results are systematically compared with available experimental data. The calculated results are also compared with theoretical results from other MM models and from relativistic mean-field model. The calculations and comparisons show that the MM model is reliable in superheavy region and that the MM model results are not very sensitive to the choice of microscopic single-particle potential.     

Alpha Decay,Shell Structure,and New Elements

We systematically analyze the experimental data of alpha decay in even-even heavy nuclei far from stability and find that the Geiger-Nuttall law brea~s for an isotopic chain when its neutron number is across a marc number or there is a deformed subshell. This break can be used to identify new magic numbers of superheavy nuclei. It is also discovered that there is a new linear relation between the logarithm of half-life and the reciprocal of the square root of decay energy for N = 126 and N = 152 isotones. It could be a new law of alpha decay for nuclei with magic neutron numbers but the physics behind it is to be explored. The significance of these researches for the search of new elements is discussed.     

Effects of shell correction on α decay properties

The shell correction effects on the α decay properties of heavy and superheavy nuclei have been studied in a macroscopic-microscopic manner. The macroscopic part is constructed from the generalized liquid drop model(GLDM), whereas the microscopic part, namely, the shell correction energy, brings about certain effects on the potential barriers and half-lives under a WKB approximation, which is emphasized in this work. The results show that the shell effects play a significant role in the estimation of the α decay half-lives within the actinide region.Predictions of the α decay half-lives are then generated for superheavy nuclei, which will provide useful information for future experiments.     

Triaxial interaction effect in the structure of ^148-158Sm

The structures of ^148-158Sm are studied in the frame of the interacting boson model. Attention is given to the triaxial interaction, and it is found that the triaxial interaction plays an important role in the detailed structure of this isotopic chain. The potential surfaces of these nuclei are also studied and the shapes of them are analysed. And it is found that though the triaxial interaction plays an important role in these nuclei, there are no stable triaxial shapes in the low-lying structures of these nuclei.     

Synthesis of superheavy nuclei with <Superscript>238</Superscript>U target

The production of superheavy nuclei with Z=108-116 via hot fusion reactions of the neutron-rich projectiles with 238U target is systematically studied.The results show that the production cross sections of superheavy nuclei do not decrease monotonously as the atomic number Z increasing.The cross sections of the superheavy nuclei at Z = 112 and 115 are enhanced as compared with the whole Z-trend in synthesis of the superheavy nuclei,which clearly illustrates that the reactions with large negative Q-value and...     

Production mechanism of superheavy nuclei in massive fusion reactions

Within the concept of the dinuclear system (DNS), a dynamical model is proposed for describing the formation of superheavy nuclei in complete fusion reactions by incorporating the coupling of the relative motion to the nucleon transfer process. The capture of two heavy colliding nuclei, the formation of the compound nucleus and the de-excitation process are calculated by using an empirical coupled channel model, solving a set of microscopically derived master equations numerically and applying statistical theory, respectively. Fusion-fission reactions and evaporation residue excitation functions of synthesizing superheavy nuclei (SHN) are investigated systematically and compared them with available experimental data. The possible factors that affecting the production cross sections of SHN are discussed in this workshop.