Shell evolution at N=20 in the constrained relativistic mean field approach

The shell evolution at N=20, a disappearing neutron magic number observed experimentally in very neutron-rich nuclides, is investigated in the constrained relativistic mean field (RMF) theory. The trend of the shell closure observed experimentally towards the neutron drip-line can be reproduced. The predicted two-neutron separation energies, neutron shell gap energies and deformation parameters of ground states are shown as well. These results are compared with the recent Hartree-Fock-Bogliubov (HFB-14) model and the available experimental data. The perspective towards a better understanding of the shell evolution is discussed.     

Theoretical Study on N = 126 Shell Evolution

The nuclei around magic number N = 126 are investigated in the deformed relativistic mean field （RMF） model with effective interactions TMA. We focus investigations on the N = 126 isotonic chain. The N = 126 shell evolution is studied by analyzing the variations of two-neutron （proton） separation energies, quadruple deformations, single particle levels etc. The good agreement of two-neutron separation energies between experimental data and calculated values is reached. The RMF theory predicts that the sizes of N = 126 shell become smaller and smaller with the increasing of proton number Z. However, the N = 126 shell exists in our calculated region all along. According to the calculated two-proton separation energies, the RMF theory suggests ^220Pu is a two-proton drip-line nucleus in the N = 126 isotonic chain.     

Theoretical Study on N = 126 Shell Evolution

The nuclei around magic number N = 126 are investigated in the deformed relativistic mean field (RMF) model with effective interactions TMA. We focus investigations on the N = 126 isotonic chain. The N = 126 shell evolution is studied by analyzing the variations of two-neutron (proton) separation energies, quadruple deformations, single particle levels etc. The good agreement of two-neutron separation energies between experimental data and calculated values is reached. The RMF theory predicts that the sizes of N = 126 shell become smaller and smaller with the increasing of proton number Z. However, the N = 126 shell exists in our calculated region all along. According to the calculated two-proton separation energies, the RMF theory suggests ²²⁰Pu is a two-proton drip-line nucleus in the N = 126 isotonic chain.     

丰中子Z=96—102同位素链的N=184闭壳

在相对论平均场理论框架下, 首先证明了对力强度存在明显的壳效应, 然后用此方法研究了Z=96—102区域内超重同位素链中中子壳封闭问题, 证明了在超重元素中,N=184处确实存在壳封闭. 并据此给出了一种检验壳封闭的新方法.     

Shears mechanism in two-dimensional cranking relativistic mean field approach

Using the new two-dimensional cranking relativistic mean field (RMF) approach, the shears mechanism of magnetic rotation based on configuration πh121/2νh-211/2 in 142Gd is microscopically and self-consistently examined by investigating the aligning angular momenta of the valence nucleons.     

Shears mechanism in two-dimensional cranking relativistic mean field approach

Using the new two-dimensional cranking relativistic mean field (RMF) approach, the shears mechanism of magnetic rotation based on configuration πh²_11/2⊙νh^－2_11/2 in ¹⁴²Gd is microscopically and self-consistently examined by investigating the aligning angular momenta of the valence nucleons.     

Investigation of the Mg isotopes using the shell-model-like approach in relativistic mean field theory

Ground state properties for Mg isotopes, including binding energies, one- and two-neutron separation energies, pairing energies, nuclear matter radii and quadrupole deformation parameters, are obtained from the self-consistent relativistic mean field (RMF) model with the pairing correlations treated by a shell-mode-like approach (SLAP), in which the particle-number is conserved and the blocking effects are treated exactly. The experimental data, including the binding energies and the one- and two-neutron separation energies, which are sensitive to the treatment of pairing correlations and block effects, are well reproduced by the RMF+SLAP calculations.     

Towards Lambda-nucleon coupling constants in relativistic mean field theory

New parameter sets for Λ-nucleon coupling in relativistic mean field theory are proposed based on nucleon-nucleon effective interaction PK1. Hypernuclear properties are described well through a systematical study. Effects of hyperon tensor coupling term on spin-orbit splitting are also investigated self-consistently.     

Towards Lambda-nucleon coupling constants in relativistic mean field theory

New parameter sets for Λ-nucleon coupling in relativistic mean field theory are proposed based on nucleon-nucleon effective interaction PK1. Hypernuclear properties are described well through a systematical study. Effects of hyperon tensor coupling term on spin-orbit splitting are also investigated self-consistently.     

Deformation constrained relativistic mean-field approach with fixed configuration and time-odd component

Deformation constrained relativistic mean-field (RMF) approach with fixed configuration and timeodd component has been developed and applied to investigate magnetic moments of light nuclei near doublyclosed shells. Taking 17O as an example, the results and discussion are given in detail.     

Properties and structure of N=Z nuclei within relativistic mean field theory

The axially deformed relativistic mean field theory with the force NLSH has been performed in the blocked BCS approximation to investigate the properties and structure of N=Z nuclei from Z=20 to Z=48. Some ground state quantities such as binding energies, quadrupole deformations, one/two-nucleon separation energies, root-mean-square （rms） radii of charge and neutron, and shell gaps have been calculated. The results suggest that large deformations can be found in medium-heavy nuclei with N=Z=38-42. The charge and neutron rms radii increase rapidly beyond the magic number N=Z=28 until Z=42 with increasing nucleon number, which is similar to isotope shift, yet beyond Z=42, they decrease dramatically as the structure changes greatly from Z=42 to Z=43. The evolution of shell gaps with proton number Z can be clearly observed. Besides the appearance of possible new shell closures, some conventional shell closures have been found to disappear in some region. In addition, we found that the Coulomb interaction is not strong enough to breakdown the shell structure of protons in the current region.     

Properties and structure of N=Z nuclei within relativistic mean field theory

The axially deformed relativistic mean field theory with the force NLSH has been performed in the blocked BCS approximation to investigate the properties and structure of N=Z nuclei from Z=20 to Z=48.Some ground state quantities such as binding energies, quadrupole deformations, one/two-nucleon separation energies, root-mean-square (rms) radii of charge and neutron, and shell gaps have been calculated.The results suggest that large deformations can be found in medium-heavy nuclei with N=Z=38-42.The charge and neutron rms radii increase rapidly beyond the magic number N=Z=28 until Z=42 with increasing nucleon number, which is similar to isotope shift, yet beyond Z=42, they decrease dramatically as the structure changes greatly from Z=42 to Z=43.The evolution of shell gaps with proton number Z can be clearly observed.Besides the appearance of possible new shell closures, some conventional shell closures have been found to disappear in some region.In addition, we found that the Coulomb interaction is not strong enough to breakdown the shell structure of protons in the current region.     

Deformation constrained relativistic mean-field approach with fixed configuration and time-odd component

Deformation constrained relativistic mean-field (RMF) approach with fixed configuration and time-odd component has been developed and applied to investigate magnetic moments of light nuclei near doubly-closed shells. Taking ¹⁷O as an example, the results and discussion are given in detail.     

A systematic study of the superdeformation of Pb isotopes with relativistic mean field theory

The microscopically constrained relativistic mean field theory is used to investigate the superdeformation for Pb isotopes. The calculations have been performed with the four different interactions NL3, PK1, TM1 and NLSH, and show that there exists a clear superdeformed minimum in the potential energy surfaces. The excitation energy, deformation and depth of the well in the     

A systematic study of the superdeformation of Pb isotopes with relativistic mean field theory

The microscopically constrained relativistic mean field theory is used to investigate the superdeformation for Pb isotopes. The calculations have been performed with the four different interactions NL3, PK1,TM1 and NLSH, and show that there exists a clear superdeformed minimum in the potential energy surfaces.The excitation energy, deformation and depth of the well in the superdeformed minimum are comparable for the four different interactions. Furthermore the trend for the change of the superdeformed excitation energy with neutron number is correctly reproduced. The calculated two-neutron separation energy in the ground state and superdeformed minimum together with their differences are in agreement with the available data.The larger energy difference appearing in the superdeformed minimum reflects a lower average level density at superdeformations for Pb isotopes.     

相对论平均场理论对Pt同位素形状演化的研究

利用形变约束的相对论平均场理论研究了Pt同位素偶-偶核的形状演化,比较了基态结合能和四极形变的理论计算值和实验值, 分析了这些核的位能曲线、单粒子能级及其随四极形变β₂ 的变化规律,发现从N=88到N=126, Pt同位素的基态变形从球形对称核经X(5)对称性核、演化为具有稳定形变的核,再演化为球形核的变化过程.其中, ^166-172Pt是近球形核, ¹⁷⁴Pt和^192-196Pt位于球形和稳定形变之间,可能具有X(5)对称性, ^176-190Pt具有稳定的变形, ^198-202Pt是近球形核, ²⁰⁴Pt是球形核,这些结果与实验一致.     

对N=184附近核的壳效应的理论研究

在形变的相对论平均场模型下采用TMA,NLZ2两套参数对Z=96—102,N=162—190区域偶偶核基态性质进行了系统的计算,对得出的理论结合能、α衰变能、四极形变参数进行了分析和讨论.这些结果同已有的SkyrmeHartreeFock计算的结果做了对比,并分析了在N=184附近的壳效应,可供以后理论或实验研究参考.     

Magnetic moments of <Superscript>33</Superscript>Mg in the time-odd relativistic mean field approach

The configuration-fixed deformation constrained relativistic mean field approach with time-odd component has been applied to investigate the ground state properties of 33Mg with effective interaction PK1.The ground state of 33Mg has been found to be prolate deformed,β2=0.23,with the odd neutron in 1/2[330] orbital and the energy -251.85 MeV which is close to the data -252.06 MeV.The magnetic moment -0.9134 μN is obtained with the effective electromagnetic current which well reproduces the data -0.7456 μN se...     

相对论平均场理论对Rn同位素链原子核基态性质的研究

在相对论平均场理论的框架下,对Rn同位素链原子核的结合能、形变、同位素位移等若干基态性质进行了较详细的研究.结果表明,理论计算结果与已有的实验数据符合较好.原子核的四极形变主要出现在远离幻数的区域(N=110-124和N=129-142).而在中子数大于幻数的区域(N=127-142),十六级形变也非常明显.对电荷半径的研究显示,Rn同位素链的同位素位移曲线的斜率在中子幻数处出现明显的变化. 关键词： 相对论平均场理论 电荷半径 同位素位移 单粒子能级     

超重核的壳结构

在相对论连续谱Hartree Bogoliubov(RCHB)理论框架下,在质子数Z=100—140和中子数N=Z+30—2Z+32等偶偶核中进行了超重球形双幻核的探索.采用的有效相互作用为NL1,NL3,NLSH,TM1,TW 99,DD ME1,PK1和PK1R.基于对双核子分离能(S2p和S2n)、双核子能隙(δ2p和δ2n)、壳修正能量(Epshell)、对能(Eppair和Enpair)和有效对能隙(Δp和Δn)等物理量和能shell和En级结构的分析,预言了可能的质子幻数和中子幻数,并观察到在超重核区壳的弱化现象. The magic proton and neutron numbers are searched in the superheavy region with proton number Z=100 —140 and neutron number N=(Z+30) — (2Z+32) by the relativistic continuum Hartree-Bogoliubov (RCHB) theory with interactions NL1, NL3, NLSH, TM1, TW99, DD-ME1, PK1, and PK1R. Based on the two-nucleon separation energies S_(2p )and S_(2n) , the two-nucleon gaps δ_(2p) and δ_(2n), the shell correction energies E~p_(shell) and E~n_(shell), the pairing energies E~p_(pair) and E~n_(pair), and...