共查询到18条相似文献,搜索用时 140 毫秒
1.
2.
基于球形与轴对称形变的相对论平均场(Relativistic Mean Field, 简称RMF)理论模型, 分别计算了Zr同位素链的基态总能量, 并根据其差值提取了形变修正能后发现, Zr同位素链丰中子区的核具有大的长椭形变, 对应的形变修正能可达到10 MeV。 利用RMF理论计算的基态能量, 在扣除液滴模型计算的结合能后, 得到了Zr同位素链的壳修正能。 通过对壳修正能的分析后发现, 形变使N=50壳效应显著减弱。 特别是在丰中子区, 大形变导致了N=50壳结构的消失。 The total binding energy of nuclei for Zr isotopic chain is calculated by the spherical and axial deformed relativistic mean field(RMF) theory respectively, and the energy contribution due to the deformation(i.e., deformation correction energy) is extracted. It is found that the neutron rich nuclei in the isotopic chain have large prolate deformation, and corresponding deformation correction energy can be up to 10 MeV. The shell correction energy is obtained by the difference between the binding energies calculated by the liquid model and those by the RMF calculations. Detailed analysis indicates that the deformation weakens the shell effect of N=50 remarkably. Especially for the neutron rich nuclei, large deformation leads to disappearance of the N=50 shell structure. 相似文献
3.
We have investigated the structure evolution of the124-134Xe isotopic chain in the framework of the proton-neutron interacting model IBM2. The positive parity spectra of the ground state, quasi-β and quasi-γ bands are reproduced well. The staggering in124-130Xe are almost completely removed and the γ band agree well with the experiment data, even for the high-spin quasi-γ states. The key quantities of the collective structure evolution, including level energies, the B(E2) transition branching ratios, and the M1 excitations to 1+1mixer-symmetry states are analyzed by comparing with the experimental data. The parameters for representation of the Oπν(6) and SU πν(3) features in isotopes are examined. Both experimental data and theoretical results show that the shape phase transition of124 134Xe isotopic chain is from the SU πν(3)(triaxial rotation) to the Uπν(5)(vibration motion) with a considerable constituent of the Oπν(6) symmetry(γ-unstable rotation), where the shape phase transition rapidly takes place between the neutron number N = 76 and N = 78. 相似文献
4.
ZHANG Jin-Fu LU Li-Jun BAI Hong-Bo 《理论物理通讯》2007,47(4):705-710
Comparing with the predictions of the transitional dynamical symmetry E(5) proposed by Iachello [Phys. Rev. Lett. 85 (2000) 3580], the critical behaviors from U(5)-0(6) are studied in the space of two control parameters in the interacting boson model. A simple shape phase diagram has been presented. It is found that E(5) predictions cannot be exactly reproduced by our calculations and that the best agreement is close to the calculations with boson number N = 9. By comparing with experimental data on E(5)-like nuclei, we find that E(5) predictions and IBM calculations can reproduce the energy ratios and E2 transition ones. 相似文献
5.
A.N.Behkami M.N.Nasrabadi 《理论物理通讯》2002,37(4):457-460
The level densities of even-odd and even-even isotopes^161,162Dy,^166Er and ^171,172Yb were calculated using microscopic theory of interacting fermions and compared with experiments.It is found that the data can be well reproduced with level density formalism for nuclei with static deformation.The nuclear temperature as well as the reproduced with level density formalism for nuclei with static deformation.The nuclear temperature as well as the entropy of nuclear system as a function of excitation energy has been extracted from the BCS theory.It is shown that the entropy exhibits an S-formed shape as a function of excitation energy.This is interpreted as a phase transition.Procedure of treating the even-odd and even-even nuclear systems has been presented and discussed. 相似文献
6.
Based on the tight-binding approximation, analytical solutions of the energy dispersion and band gap of armchair-edge graphene nanoribbons (AGNRs) under uniaxial strains are derived. Subsequent numerical results on band gap are found to be consistent with the analytical solutions. It is shown that the energy gap of AGNRs is sensitive to the uniaxial strains and is predicted to change with a V shape as a function of the applied uniaxial strain. It is interesting to find that the uniaxial strain could induce metal-semiconductor transition for the AGNRs with a width of n=3m+2 ((3m + 2)-AGNRs) and semiconductor-metal-semiconductor phase transition for the (3m + 1)-AGNRs, but no phase transition is induced for the 3m-AGNRs. 相似文献
7.
原子核的形状相变 总被引:2,自引:0,他引:2
简要回顾原子核形状相变研究的现状,并将相干态理论与角动量投影方法相结合,在不区分质子玻色子和中子玻色子的相互作用玻色子模型(IBM-1)框架下,对角动量驱动的轴对称情况下的具有U(5)、SU(3)对称性以及两种对称性之间过渡区的原子核的形状相变进行了具体研究。We review the status of the research of nuclear shape phase transitions in this paper. Meanwhile, by taking the coherent state theory and angular momentum projection method, we study the shape phase transitions of axially symmetric even-even nuclei with U(5) symmetry, SU(3) symmetry and those in the transitional region of the two symmetries in the framework of Interacting Boson Model-1 (IBM-1), which does not distinguish the proton bosons from neutron bosons. 相似文献
8.
基于中子分离能的分析 ,Ozawa等提出丰中子轻核存在新幻数 N=1 6.对 N=1 6同中子素进行了形变和球形的相对论平均场计算 .相对论平均场的数值结果表明N=1 6同中子素有形状相变.这是一些丰中子核新幻数出现的可能原因. Based on the analysis of neutron-separation energies, Ozawa et al proposed a new magic number N =16 in light neutron-rich nuclei. The deformed and spherical relativistic mean-field(RMF) calculations have been carried out for N =16 isotones. The numerical relativistic mean-field results show there is a shape transition in N =16 isotones. This is the possible cause of the appearance of the new magic number in someneutron-rich nuclei. 相似文献
9.
The potential energy surfaces of even-even 142-156Ba are investigated in the constrained reflectionasymmetric relativistic mean-field approach with parameter set PK1. It is shown that for the ground states, 142Ba is near spherical,156Ba well quadrupole-deformed, and in between 144-154Ba octupole deformed. In particular, the nuclei 148,150Ba with N=92, 94 have the largest octupole deformations. By including the octupole degree of freedom, energy gaps N = 88, N = 94 and Z = 56 near Fermi surfaces for the singleparticle levels in 148Ba with β2 ~ 0.26 and β3 ~ 0.17 are found. Furthermore, the performance of the octupole deformation driving pairs (ν2f7/2, ν1i13/2) and (π2d5/2, π1h11/2) is demonstrated by analyzing the singleparticle levels near Fermi surfaces in 148Ba. 相似文献
10.
The E-Gamma Over Spin (E-GOS) analysis method is applied to the study of the shape phase transition of neutron-rich even-even light nuclei with Z=20-28. Some valuable results are gained through analysing E-GOS curves of Ca, Ti, Cr, Fe and Ni nuclei. 相似文献
11.
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. 相似文献
12.
《中国物理C(英文版)》2015,(10)
Some binding energy related quantities serving as effective order parameters have been used to analyze the shape phase transition in the odd Sm nuclei. It is found that the signals of phase transition in the odd Sm nuclei are greatly enhanced in contrast to the even Sm nuclei. A further analysis shows that the transitional behaviors related to pairing in the Sm nuclei can be well described by the mean field plus pairing interaction model, with a monotonic decrease in the pairing strength G. 相似文献
13.
14.
Systematic Analysis of E(5) Critical-Point Nuclei in A~130 Region with Relativistic Mean Field Theory 下载免费PDF全文
The shape phase transition between spherical U(5) and γ-unstable O(6) nuclei is investigated systemically for the nuclei in the A~130 region by the constrained relativistic mean field theory. By examining potential energy surfaces and neutron Fermi energies, we suggest that 136Ba and 132,134Xe are possible nuclei with E(5) symmetry, which is favored by the observed ratio R4/2=(E+41-E+01)/(E+21-E+01). While the RMF predicted E(5) symmetry or 128,130,132Te cannot be supported by the observed ratio R4/2. Whether these nuclei are critical-point nuclei should further be examined in experiments. 相似文献
15.
16.
S. Akkoyun T. Bayram S. O. Kara N. Yildiz 《Physics of Particles and Nuclei Letters》2013,10(6):528-534
Nuclear shape transition has been actively studied in the past decade. In particular, the understanding of this phenomenon from a microscopic point of view is of great importance. Because of this reason, many works have been employed to investigate shape phase transition in nuclei within the relativistic and nonrelativistic mean field models by examining potential energy curves (PECs). In this paper, by using layered feed-forward neural networks (LFNNs), we have constructed consistent empirical physical formulas (EPFs) for the PECs of 38–66Ti calculated by the Hartree-Fock-Bogoliubov (HFB) method with SLy4 Skyrme forces. It has been seen that the PECs obtained by neural network method are compatible with those of HFB calculations. 相似文献
17.
Shape transitions as a function of angular momentum in even–even krypton isotopes with A?=?72–84 have been investigated using the cranked Nilsson–Strutinsky method. The Jacobi shape transition from noncollective oblate to super or hyperdeformed collective prolate or triaxial shape taking place in rotating nuclei as in the case of gravitating rotating stars is studied in krypton isotopes. The cranked Nilsson–Strutinsky method with a method of tuning the angular velocity to get the fixed spins is used in the calculations. Our results show that all the krypton isotopes considered in this study are the good candidates for detecting the Jacobi shape transition. Shape evolutions as a function of spin and temperature with thermal fluctuations are studied using the Landau theory of phase transitions. The constants appearing in the Landau expression for the free energy are determined by using the free energy surfaces at ω?=?0 calculated by the Strutinsky method. We show that in the presence of thermal fluctuations, the averaged shapes obtained for the considered isotopes differ from the most probable shapes. The sharp Jacobi transitions are modified due to the effect of thermal fluctuations. 相似文献
18.
在Debye-Hückel屏蔽近似下,基于相对论Dirac-Fock方法,发展了包括等离子体屏蔽效应的自洽场计算程序.使用该程序研究了等离子体屏蔽效应对类氢离子能级结构和辐射跃迁性质的影响.结果表明,当原子处于等离子体环境中,所有束缚态能级向连续态移动, 移动量随着屏蔽长度的减小而增大.振子强度随屏蔽长度的变化也表现出了相同的规律.进一步分析了相对论效应和等离子体屏蔽效应的耦合,发现对于中Z元素,相对论效应和等离子体屏蔽效应存在较强的耦合.讨论了等离子体屏蔽效应对原子精细结构能级的影响.计算发现,由于等离子体屏蔽效应,原子的能级次序发生了变化,κ简并被消除.
关键词:
等离子体屏蔽
Debye-Hückel 模型
能级结构
跃迁概率 相似文献