平均场加区分质子和中子的邻近轨道对力模型及对超铀区核的统一描述

利用严格可解的平均场加区分质子和中子的邻近轨道相互作用对力模型,对超铀区部分大形变核进行了统一的描述.计算了^227—233Th,^232—239U,^236—243Pu同位素和同中异质素²²⁸Ra-²²⁹Ac-²³⁰Th-²³¹Pa-²³²U,²³²Th-²³³Pa-²³⁴U-²³⁵Np-²³⁶Pu,²³⁶U-²³⁷Np-²³⁸Puv-²³⁹Am的结合能,对激发能和奇偶能差并与相应核的实验值进行了比较     

相对论平均场理论框架下对能的系统研究

在相对论平均场模型的框架内,沿原子核的稳定线,以每隔4个质子或中子提取样本的方法,计算了核谱图上数十个原子核的对能,特别是研究了氧同位素偶-偶核的对能随核子数的变化规律,发现在固定能隙Δ的条件下,对能的大小和核的壳结构有关,由此提出了一种检验闭壳效应的简便方法,进而发现中子数N=6不仅在轻核的丰中子区是一个新幻数,而且在丰质子区也是一个可能的新幻数. 关键词： 相对论平均场模型 对能 能隙 幻数     

一种推广对力模型及在大形变核中的应用

总结了可描述大形变原子核运动的Nilsson平均场加推广的对力相互作用的可解模型.该模型在对力强度较弱的区域仍然以单体和两体相互作用为主.但随着对力强度的增加,高阶相互作用的修正将逐渐变得重要.通过对同位素154—171Yb奇偶质量差的数值拟合显示,该新模型可说明大形变核的运动规律.     

Er，Yb和Hf同位素的基态占有率（英文）

应用严格求解的Nilsson 平均场加推广对力模型,在同时考虑质子-质子和中子-中子间对力相互作用的情况下,对稀土区的152-164Er,154-166Yb 和156-168Hf 核素的结合能、奇偶能差、低激发态转动惯量等基态性质进行系统的统一描述。通过计算结果与实验数值比较分析显示,对力相互作用在阐明以上核素能谱的基态性质中起到了关键的作用。应用拟合上述物理量所确定的模型参数,对156-162Yb 核素基态中价核子配成角动量J = 0,1,… ,12的价核子对占有率的计算结果显示,配成角动量为偶数价核子对的占有率远远高于配成角动量为奇数价核子对的占有率,其数值结果揭示了配成角动量为S,D和G的价核子对在所考虑的核素基态性质中占主导地位。The Nilsson mean-field plus extended-pairing model for deformed nuclei is applied to describe the ground-state properties of selected rare-earth nuclei. Binding energies, even-odd mass differences, moments of inertia for the ground-state band of 152-164Er, 154-166Yb, and 156-168Hf are calculated systematically in the model employing both proton-proton and neutron-neutron pairing interactions. In comparison with the corresponding experimental data, it is shown that for these rare-earth nuclei, pairing interaction is crucial in elucidating the properties of the ground state. With model parameters determined by fitting the energies of these states, ground-state occupation probabilities of valence nucleon pairs with angular momentum J =0,1, …,12 for even-even 156-162Yb are calculated. It is inferred that the occupation probabilities of valence nucleon pairs with even angular momenta are much higher than those of valence nucleon pairs with odd angular momenta. The results clearly indicate that S, D, and G valence nucleon pairs dominate in the ground state of these nuclei.     

平均场加邻近轨道对力模型描述N=94同中异质素性质

利用严格可解的Nilsson平均场加邻近轨道对力模型,在区分质子和中子情况下,研究了大形变核的性质,主要计算了中子数为N=94的同中异质素的结合能、奇偶能差和转动惯量,并与相应的实验值进行了系统比较,结果表明此模型可以合理描述这些性质,正确反映原子核奇偶性质的变化规律。然后以偶偶核160Dy为例,研究了基态中各角动量J=0,1,...,12价核子对的占有率。结果表明,偶角动量占有率远高于奇角动量占有率,其中S,D,G价核子对各组份在基态波函数中是主要的。The Nilsson mean-field plus the nearest orbit pairing model for deformed nuclei is applied to investigate systematically the properties of the N=94 nuclei,employing both proton-proton and neutron-neutron pairing interactions.The binding energies,even-odd mass differences,moments of inertia are calculated and compared with the corresponding experimental data.The results show that this model can reasonably describe these properties.Further,the ground-state occupation probabilities of valence nucleon pairs with angular momentum J=0,1,...,12 for even-even 160Dy are calculated,and the results show that it is much higher for the even angular momenta than the odd angular momenta,and the S,D,G components in the ground-state wave function are dominant.     

The neutron-proton pairing and the moments of inertia of the rare earth even-even nuclei

In this study, the possible effect of the neutron-proton pairing interaction in the heavy nuclei has been investigated in the framework of the BCS model by making a simple approximation. This effect has been searched realistically by calculating the moments of inertia of deformed even-even nuclei. Calculations show that the moments of inertia of rare earth nuclei changed dramatically and approached the experimental values.     

The quadrupole plus pairing interaction model in large configuration space for W,Os and Pt nuclei

The equilibrium deformations of tungsten, osmium and platinum nuclei are studied with the self-consistent quadrupole plus pairing interaction model by considering all the nucleons in nucleus explicitly. It is shown that similar results can be obtained by performing calculations with or without the assumption of an inert core. The only difference is in the strength of the quadrupole and pairing interactions to be employed in the respective calculations. The experimental static quadrupole moments and theB (E2) values are correctly reproduced by performing calculations with bare nucleon charge for all the nucleons.     

Solution to the eigenstates of pairing Hamiltonian in finite nuclei

We apply the algebraic Bethe technique to the nuclear pairing problem with certain limits. We obtain the exact energies and eigenstates, and find the symmetry between the states corresponding to less and more than half full shell. We also proved that the problem of solving BAE can be transformed into the problem of finding the roots of a hypergeometric polynomial, which is much simpler.     

Solution to the eigenstates of pairing Hamiltonian in finite nuclei

We apply the algebraic Bethe technique to the nuclear pairing problem with certain limits. We obtain the exact energies and eigenstates, and find the symmetry between the states corresponding to less and more than half full shell. We also proved that the problem of solving BAE can be transformed into the problem of finding the roots of a hypergeometric polynomial, which is much     

平均场加邻近轨道相互作用对力模型在大形变核中的应用

利用严格可解的平均场加邻近轨道相互作用对力模型来描述大形变核.将该模型应用于稀土区和超铀区的核素.计算了^158—171Er,^160—178Yb,^170—183Hf,^226—234Th, ^230—240U,及^236—243Pu同位素的结合能和对激发能,并与实验结果进行了比较     

用相对论平均场理论研究近滴线区原子核传统幻数的消失和新幻数的产生

提出了一种从理论上检验壳效应的方法.在考虑了由Bardeen，Cooper和Schrieffer提出的金属超导理论(BCS方法)的相对论平均场理论框架内，通过计算粒子数的涨落，发现涨落的大小和核的壳结构有紧密的关系，进而研究了滴线区一些传统幻数的消失和新幻数的产生. 关键词： 相对论平均场理论 粒子数涨落 幻数 壳效应     

A mean-field equation of motion for the dynamic Ising model

A mean-field type of approximation is used to derive two differential equations, one approximately representing the average behavior of the Ising model with Glauber (spin-flip) stochastic dynamics, and the other doing the same for Kawasaki (spin-exchange) dynamics. The proposed new equations are compared with the Cahn-Allen and Cahn-Hilliard equations representing the same systems and with information about the exact behavior of the microscopic models.     

Investigation on the deformation of Ne and Mg isotope chains within relativistic mean-field model

Ne and Mg isotope chains are investigated based on constrained calculations in the framework of a deformed relativistic mean-field （RMF） model with the NL075 parameter set. The calculated quadrupole deformation and binding energy are compared with other theoretical results as well as the available experimental data. It shows that the calculated deformations of Ne and Mg with the NL075 are more accurate than those obtained with the NL-SH. It is predicted that ^19,29,32Ne and ^20,31Mg maybe have a triaxial deformation and ^25-28Ne and ^27-30Mg exhibit a shape coexistence probably. The closure effect of neutron number N=8 for ^20Mg is predicted to be very weak.     

关于原子核奇偶质量差和能隙的研究

系统分析了奇偶核质量差公式的适用性及与能隙参数的关系. 计算了核素Sn和Pb附近10个同位素链的中子奇偶质量差Δ(3)n, 发现壳效应、核子对相互作用、核的形变都会明显影响Δ(3)n的数值, 并在此基础上, 给出了一个修正的奇偶核质量差公式.     

Toward precision mass measurements of neutron-rich nuclei relevant to r-process nucleosynthesis

The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies. Of all the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is a key quantity for revealing the origin of heavy elements beyond iron. Although the precise determination of this property is a great challenge, enormous progress has been made in recent decades, and it has contributed significantly to both nuclear structure and astrophysical nucleosynthesis studies. In this review, we first survey our present knowledge of the nuclear mass surface, emphasizing the importance of nuclear mass precision in r-process calculations. We then discuss recent progress in various methods of nuclear mass measurement with a few selected examples. For each method, we focus on recent breakthroughs and discuss possible ways of improving the weighing of r-process nuclides.     

Isospin dependent properties of the isotopic chains of Scandium and Titanium nuclei within the relativistic mean-field formalism

Density-dependent nuclear symmetry energy is directly related to isospin asymmetry for finite and infinite nuclear systems. It is critical to determine the coefficients of symmetry energy and their related observables because they hold great importance in different areas of nuclear physics, such as the analysis of the structure of ground state exotic nuclei and neutron star studies. The ground state bulk properties of Scandium (Z = 21) and Titanium (Z = 22) nuclei are calculated, such as their nuclear binding energy (begin{document}$ B.E. $end{document}), quadrupole deformation (begin{document}$ beta_2 $end{document}), two-neutron separation energy (begin{document}$ S_{ {2n}} $end{document}), differential variation in the two-neutron separation energy (begin{document}$ {rm d}S_{ {2n}} $end{document}), and root-mean-square charge radius (begin{document}$ r_{rm ch} $end{document}). The isospin properties, namely the coefficient of nuclear symmetry energy and its components, such as the surface and volume symmetry energy of a finite isotopic chain, from the corresponding quantities of infinite nuclear matter, are also estimated. Finally, we correlate the neutron-skin thickness with the coefficient of symmetry energy and the related observables corresponding to the isotopic chains of these nuclei. The coherent density fluctuation model (CDFM) is used to estimate the isospin-dependent properties of finite nuclei, such as symmetry energy, surface symmetry energy, and volume symmetry energy, from their corresponding component in infinite nuclear matter. The relativistic mean-field (RMF) formalism with non-linear NL3 and relativistic-Hartree-Bogoliubov theory with density-dependent DD-ME2 interaction parameters are employed in the analysis. The weight function begin{document}$ vert {cal{F}}(x) vert^{2} $end{document} is estimated using the total density of each nucleus, which in turn is used with the nuclear matter quantities to obtain the effective symmetry energy and its components in finite nuclei. We calculate the ground state bulk properties, such as nuclear binding energy, quadrupole deformation, two-neutron separation energy, differential variation in the two-neutron separation energy, and root-mean-square charge radius, for the Sc- and Ti- isotopic chains using the non-linear NL3 and density-dependent DD-ME2 parameter sets. Furthermore, the ground state density distributions are used within the CDFM to obtain the effective surface properties, such as symmetry energy and its components, namely volume and surface symmetry energy, for both the parameter sets. The calculated quantities are used to understand the isospin dependent structural properties of finite nuclei near and beyond the drip line, which broadens the scope of discovering new magicity along the isotopic chains. A shape transition is observed from spherical to prolate near begin{document}$ N geq $end{document} 44 and begin{document}$ N geq $end{document} 40 for the Sc- and Ti- isotopic chains, respectively. Notable signatures of shell and/or sub-shell closures are found for the magic neutron numbers N = 20 and 28 for both isotopic chains using the nuclear bulk and isospin quantities. In addition to these, a few shell/sub-shell closure signatures are observed near the drip-line region at N = 34 and 50 by following the surface/isospin dependent observables, namely symmetry energy and its component, for both the isotopic chain of odd-A Sc- and even-even Ti- nuclei.     

Crystal potential model for the description of crystalline electric field effects in rare earth metals and intermetallics

A crystal potential model is suggested. It allows us to interpret crystalline electric field effects in optical, EPR, NMR, NGR and neutron spectroscopy measurements in rare earth metals and intermetallics. The crystal potential character and space distribution are discussed. The model is used for the theoretical interpretation of the effects of the crystalline field in the compound PrAl₃.     

Effect of Wigner energy on the symmetry energy coefficient in nuclei

The nuclear symmetry energy coefficient(including the coefficient a_(sym)~((4)) of the I~4 term) of finite nuclei is extracted by using the differences of available experimental binding energies of isobaric nuclei.It is found that the extracted symmetry energy coefficient a_(sym)~*(A,I) decreases with increasing isospin asymmetry I,which is mainly caused by Wigner correction,since e_(sym)~* is the summation of the traditional symmetry energy e_(sym) and the Wigner energy ew.We obtain the optimal values J = 30.25±0.10 MeV,a_(ss)=56.18±1.25 MeV,a_(sym)~((4)) = 8.33±1.21 MeV and the Wigner parameter x= 2.38 ±0.12 through a polynomial fit to 2240 measured binding energies for nuclei with20 ≤ A ≤ 261 with an rms deviation of 23.42 keV.We also find that the volume symmetry coefficient J■ 30 MeV is insensitive to the value x,whereas the surface symmetry coefficient a_(ss) and the coefficient a_(sym)~((4)) are very sensitive to the value of x in the range 1≤x≤4.The contribution of the a_(sym)~((4)) term increases rapidly with increasing isospin asymmetry I.For very neutron-rich nuclei,the contribution of the a_(sym)~((4)) term will play an important role.     

相对论平均场模型对奇-偶超重核基态性质的系统研究

在形变的相对论平均场模型下,采用NL-Z2,TMA两套参数对质子数为103—109的奇–偶核基态性质进行了系统的计算,并将理论计算的结合能、α衰变能与已知的实验数据进行对比,发现两者符合得很好,肯定了相对论平均场模型对超重核研究的可靠性,同时对未知核素基态性质的计算结果可供未来的超重核理论和实验研究参考.     

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.