Coulomb effects on the formation of proton halo nuclei

This paper makes some qualitative and quantitative analyses about halo formation rules of some mirror nuclei with the relativistic mean-field （RMF） theory and the Woods Saxon mean-field model. By analysing two opposite effects of Coulomb interaction on the proton halo formation, it finds that the energy level shift has a larger contribution than that of the Coulomb barrier when the mass number A is small, the hindrance of the Coulomb barrier becomes more obvious with the increase of the mass number A, and the overall effect of the Coulomb interaction almost disappears when A ≈ 39 as its two effects counteract with each other.

Structure of Halo Nuclei

A self-similar-structure shell modct （SSM） is proposed to extend the conven-tional shell model （SM） calculation to study halo nuclei.The exotic structures of 11Liand 6He nuclei are reproduced by means of SSM.The neutron halo of 11Li comes fromthe spin-orbit term and the thick neutron skin of 6He arises from the different quantumnumbers Nn and Np（N=2n+1） in SSM.

Rotating deformed halo nuclei and shape decoupling effects

To explore the rotational excitation of deformed halo nuclei,the angular momentum projection(AMP)has been implemented in the deformed relativistic Hartree-Bogoliubov theory in continuum(DRHBc),in which both the mean field and collective wave functions are expanded in terms of Dirac WoodsSaxon basis.The DRHBc+AMP approach self-consistently describes the coupling between single particle bound states and the continuum not only in the ground state but also in rotational states.The rotational modes of deformed halos in ^(42,44)Mg are investigated by studying properties of rotational states such as the excitation energy,configuration,and density distribution.Our study demonstrates that the deformed halo structure persists from the ground state in the intrinsic frame to collective states.Especially,the typical behavior of shape decoupling effects in rotating deformed halo nuclei is revealed.

Three-body model for neutron-halo nuclei

The neutron-halo nuclei, ^11Li, ^14Be, and ^17B, are studied in the three-body model. The Yukawainteraction is used to describe the interaction of the two-body subsystem. For given parameters ot the twobody interaction, the properties of these neutron-halo nuclei are calculated with the Faddeev equations and the results are compared with those in the variational method. It is shown that the method of the Faddeev equations is more accurate. Then the dependencies of the two- and three-body energies on the parameters are studied. We find numerically that two- and three-body correlations differ greatly from each other with the variation of the intrinsic force range.

Density-dependent potential for multi-neutron halo nuclei

We apply a simple density-dependent potential model to the three-body calculation of the groundstate structure of drip-line nuclei with a weakly bound core. The hyperspherical harmonics method is used to solve the Faddeev equations. There are no undetermined potential parameters in this calculation. We find that for the halo nuclei with a weakly-bound core, the calculated properties of the ground-state structure are in better agreement with experimental data than the results calculated from the standard Woods-Saxon and Gauss type potentials. We also successfully reproduce the experimental cross sections by using the density calculated from this method. This may be explained by the fact that the simple Fermi or Gaussian function can not exactly describe the density distribution of the drip-line nuclei.

Structures of Light Neutron-Rich Nuclei with Orbit-Orbit Coupling

The properties of N = 7, 8, 9 isotones with Z = 4 - 8 are studied in the framework of the single-particle shell model. A tentative orbit-orbit coupling is introduced in the average nuclear potential. Calculations give a unified description of the structures of N- 7, 8, 9 isotones. The neutron level inversion in N = 7 and N = 9 isotones is discussed. The ground-state level inversion in 11Be and ^15C is reproduced. The inversion between 2s1/2 and 1d5/2 neutron levels in 14B and 13Be is predicted. The possible halo structures in N = 7 and N = 9 isotones are analysed. The numerical results confirm the one-neutron halo structures in ^11Be（2s1/2）, ^11 Be（1p1/2）, ^12B（2s1/2）, ^133C（2s1/2）, ^14B（2s1/2） and ^15C（2s1/2）. The study implies that the attempt of considering orbit orbit interaction in the shell model may be a feasible way to explain the anomalous properties of exotic light nuclei.

Proton Elastic Scattering from ^14Be and Halo Effects

The elastic scattering of p-^14Be system at Elab = 200 MeV is evaluated within the relativistic impulse approximation. We discuss the effects of the halo neutrons on the three observables of the elastic scattering system, such as differential cross section dσ/ dΩ, analyzing power Ay and spin rotation Q. The results of the three observables of the elastic scattering of p-^14Be system are compared with those of p-^12C and p-^16O systems at the same energy as E1ab = 200 MeV. We have found that in the small angular region the Ay and Q, as well as dσ/dΩ, are quite sensitive to the nucleon density distributions on the surface of the target nucleus and offer some unique behaviors of halo nuclei.

Effects of Distorted Wave on Proton Elastic Scattering from Light Nuclei at 200 MeV

The distorted wave is introduced into the relativistic impulse approximation to generate the Dirac optical potentials for proton elastic scattering. Those potentials, produced by folding the target ground state wavefunction with the free nucleon-nucleon interactions, are used to reevaluate scattering observables, such as differential cross section, analysing power and spin rotation function, for proton elastic scattering from ^12C and ^16O at Elab = 200 MeV, respectively. The inclusion of the distorted wave in the original relativistic impulse approximation has brought out better results of the observables, especially at small scattering angles.

Cross Sections of Elastic Electron and Positron Scattering from Proton-Rich Nuclei

We investigate the cross sections of the elastic electron or positron scat tering from 208 Pb, ^12C ^12,16O and ^28,32S by the relativistic partial-wave expansion method using the static charge density distribution from the self-consistent relativistic mean fiel model and also calculate the charge form factor for ^12＇16O and ^28,32S. The numerical results are compared with the available data. Calculations indicate that the extended charge density distributions of ^12O and ^28S have observable effects on the cross sections of the electron or positron scattering as well as the charge form factors.

不稳定核奇特结构研究的发展与展望

原子核是一个由核力主导的量子多体复杂系统,相对容易发生形变、转动振动、裂变、集团共振等整体性变化。过去的三十多年,我们见证了实验室可达的核素版图的迅速扩大,以及在不稳定核研究中的一系列新发现和新突破。典型的例子如晕核及其关联的奇特结构现象、采用消色差磁谱仪实现弱流条件下在束γ谱学测量从而观察不稳定核区壳演化、不稳定核基本性质测量与新幻数、丰富的多核子关联与集团和分子结构等。未来在新的核素版图区域,特别是中重质量丰中子核区,会涉及极端奇特结构、核天体r-过程、攀登超重岛路径等重大科学问题。为了探索这些问题,世界各科技大国都在建设能够产生远离稳定线放射性核束的大科学装置,不稳定核奇特结构的研究也将迎来更大的突破。

变形核中的晕现象与形状退耦合

随着放射性核束物理的快速发展,在远离β稳定线的原子核中发现或者预言了很多奇特核结构现象,包括变形晕、变形晕核中形状退耦合等。对这些奇特核现象的研究是当前核物理的重要前沿领域。协变密度泛函理论是目前最为成功的用于描述原子核结构性质的理论模型之一。本文介绍基于协变密度泛函理论对变形晕核研究的结果和进展。考虑连续谱效应的形变相对论Hartree-Bogoliubov理论实现了变形晕核的微观自洽描述并预言了镁-44中的变形晕和核芯与晕的形状退耦合现象。之后,该理论还被用于研究硼和碳等同位素链原子核中的变形晕现象。基于该理论的角动量投影计算表明:在变形晕核的低激发转动态中依然存在晕现象以及形状退耦合现象。

晕核^6He（25MeV／u）在^9Be上的弹性散射研究

分析了北京大学核物理实验小组在日本RIKEN实验室完成的 25MeV/u6He和9Be的弹性散射实验数据, 得到了弹性散射微分截面角分布. 利用双折叠模型, 并通过拟合弹性散射微分截面得到了此弹靶体系在此能量下的弹性散射光学势.

晕核的标度定律

利用重叠函数的渐近归一化常数(ANC)计算了一系列核的价核子处于核外的几率及价核子密度分布的均方根半径〈r2〉1/2.由于实验上抽取的核ANC近似与模型参数无关,因此由核ANC计算的核外几率和均方根半径是考察晕核的可靠且有效的观察量.依价核子处于核外的几率大于50%为条件,证实了一些核为晕核,且给出了比较宽松的晕核出现的条件.此外,还用〈r2〉/R2≥1.5及〈r2〉1/2/rc≥2.0为判据考察了一系列晕核候选者.最后,利用r2算符在有限方势阱中的预期值给出了晕核的标度定律.

P同位素的质子滴线核研究

研究了在相对论平均场近似下P同位素的滴线核的性质,首先在理论上探讨了25P作为P的滴线核存在的可能性及其可能具有的质子晕结构,然后给出了在兰州放射性束流装置上25P的实验鉴别结果.

^(69)Ni、^(70)Ni激发态的相对论平均场研究

在球形相对论平均场模型下,采用NL3相互作用,对69N i、70N i基态以及第一、第二激发态进行计算.从核子的半径、价核子的激发能以及中子和质子的密度分布,得出结论:在69N i7、0N i第一和第二激发态都可能存在中子晕现象.

用相对论性密度依赖Hartree方法研究两体关联在晕核中的效应

用相对论性密度依赖的 Hartree方法研究晕核的基本性质 ,在晕核的唯象图景中 ,作为剩余相互作用的对关联效应对核晕的描述有关键作用 .用只有一个自由参数的模型 ,同时给出了晕核11Li,11Be和 19C的分离能和质量密度分布 。

新核素与奇特核

在原子核物理学发展的早期 ,物理学家就已开始尝试人工制造比铀 (原子序数Z =92 )还重的新元素。经过多年努力 ,特别是有了重离子加速器以后 ,这个研究领域取得了长足的发展。利用各种精心设计的实验 ,产生和鉴定了许多新的过渡区核素以及Z≥ 10 3的超重元素。这个领域的最新工作还包括对极弱束缚核系统的研究 ,例如晕核、皮核以及其它结构奇特的原子核。这些奇特核具有很大的中子数 质子数比值N Z ,并且表现出未曾预料到的结构和全新的性质。迄今尚不很清楚 ,当中子盈余或质子盈余变得很大时 ,原子核作为一个强相互作用多粒子系统 ,如何由正常结构演化到上述奇特结构 ?

Dirac Optical Potential of p-^14Be and Pronounced “Long-Tail” Shape

The Dirac optical potential for p-14Be elastic scattering is evaluated by the relativistic impulse approximation. Each of the real part and the imaginary part of the potential shows a pronounced "long tail" for the proton elastic scattering from halo nucleus 14Be compared with the potentials for proton scattering from its adjacent nuclei 12C and 16O, which do not have halo structures. This kind of "long tail" phenomenon suggests another signature for halo nuclei.

晕核和推广的Glauber理论

简要介绍了中子晕和质子晕研究的最新实验进展 ,同时 ,讨论了近年来发展的同位旋 ,能量有关的具有晕核结构的 Glauber理论及它在描述晕核与核散射时的重要性 .

远离β稳定线奇异核性质的理论研究

回顾了对远离β稳定线奇特核性质的理论研究现状，并用相对论平均场理论研究了远离β稳定线奇特核的性质．包括轻核的中子晕和质子晕。