Level statistics for the even-even Yb isotopes

The level statistics of the even-even Yb isotopes are studied by using the energy levels calculated by the projected shell model. The spectrum of intrinsic states and band energies are also studied to discuss the generation of chaoticity. The energy dependence of the chaoticity is investigated, and a chaos to order transition is found.     

Level statistics for the even-even Yb isotopes

The level statistics of the even-even Yb isotopes are studied by using the energy levels calculated by the projected shell model. The spectrum of intrinsic states and band energies are also studied to discuss the generation of chaoticity. The energy dependence of the chaoticity is investigated, and a chaos to order transition is found.     

偶偶 Ra 同位素的八极形变研究

用反射不对称的相对论平均场理论(RAS-RMF)对偶偶Ra同位素的八极形变进行了系统研究,并与实验数据和有限力程小液滴模型(FRDM)结果进行了比较.结果表明：RAS-RMF理论很好地描述了Ra同位素的基态性质,计算的结合能、双中子分离能和形变与实验数据和FRDM一致.RAS-RMF理论获得的中子、质子密度分布清晰地展现出偶偶Ra同位素由球形逐渐转变为八极形变,到四极形变的过程,与实验观察的八极形变不稳定现象一致. 关键词： 反射不对称平均场(RAS-RMF) 八极形变 偶偶核     

偶偶 Ra 同位素的八极形变研究

用反射不对称的相对论平均场理论(RAS-RMF)对偶偶Ra同位素的八极形变进行了系统研究,并与实验数据和有限力程小液滴模型(FRDM)结果进行了比较.结果表明：RAS-RMF理论很好地描述了Ra同位素的基态性质,计算的结合能、双中子分离能和形变与实验数据和FRDM一致.RAS-RMF理论获得的中子、质子密度分布清晰地展现出偶偶Ra同位素由球形逐渐转变为八极形变,到四极形变的过程,与实验观察的八极形变不稳定现象一致.     

Intruder states in even-even neutron-rich Pd isotopes

The decays of ¹¹²Rh ^g and ¹¹²Rh ^m obtained as on-line mass separated fission products have been investigated by standard β and γ spectroscopic techniques and γ-γ angular correlations. Low-lying 0⁺ and 2⁺ states are identified in the daughter nucleus ¹¹²Pd. Systematics suggests the existence of an intruder band which is the lowest in ¹¹⁰Pd, i.e. two neutrons before the midshell. Received:13 March 1998     

Description of even-even Krypton isotopes by the Interacting Boson Approximation

Energy spectra andB(E2) values of the even-even Kr isotopes^74–82Kr have been analyzed in terms of the IBA-2 model of Otsuka, Arima and Iachello [6, 7]. We can reproduce the variation of collectivity along the isotope chain by means of a consistent set of 5 parameters, essentially only one of them has been varied with neutron number. The low lying 0 ₂ ⁺ states have been found to be strongly influenced by shell effects. Predictions are given for the not yet observed gamma bands of^74,76Kr.     

Calculation of the ground state properties of even-even Sn isotopes

We investigate the ground-state properties of even-even Sn isotopes using the Skyrme-Hartree-Fock (SHF) and Skyrme-Hartree-Fock-Bogolyubov (SHFB) methods with SKM* and SLy4 force parameters. We focus on isotopes of even-even Sn because these isotopes are vital to the structural studies of unstable nuclei taking place at the electron radioactive-ion collider at RIKEN. In the present paper, we calculate the binding energies per particle, the rms nuclear charge radii, the rms nuclear proton density radii, and the rms nuclear neutron density radii, for even-even Sn isotopes, using the SHF and SHFB methods. We compare our results with experimental data and with the results of relativistic mean-field theory. Notably, we fit our calculated binding energies per particle to experimental results, using the aforementioned SHF methods with SKM* and SLy4 parameters     

IBM-2 calculations of some even-even selenium nuclei

In this study, we determined the most appropriate Hamiltonian that is needed for present calculations of nuclei in the A≅ 80 region by the view of interacting boson model (IBM-2). Using the best-fitted values of parameters in the Hamiltonian, we have calculated energy levels and B(E2) values for a number of transitions in some doubly even Se nuclei. The results were compared with the previous experimental and theoretical data and it is observed that they are in good agreement. The calculations have been extended to Se isotopes with A < 76 for which some B(E2) values are still not known.     

Projected SD-pair shell model study for even-even Xe isotopes

Projected SD-pair shell model is used to study the collectivity of low-lying state for even-even Xe isotopes. It is found that the collectivity can be reproduced in term of a three-parameter Hamiltonian.     

Band structure of even-even selenium isotopes in the proton-neutron interacting Boson model

Available systematic IBM calculations [1-6] for Krypton and Strontium isotopes have been extended to Selenium. The analysis in terms of the IBM is complicated by the interplay of collective and noncollective degrees of freedom. However, satisfactory agreement has been obtained forN≦42.     

Proton magic even-even isotopes and giant halos of Ca isotopes with relativistic continuum Hartree-Bogoliubov theory

We study the proton magic O, Ca, Ni, Zr, Sn, and Pb isotope chains from the proton drip line to the neutron drip line with the relativistic continuum Hartree-Bogoliubov (RCHB) theory. Particulary, we study in detail the properties of even-even Ca isotopes due to the appearance of giant halos in neutron rich Ca nuclei near the neutron drip line. The RCHB theory is able to reproduce the experimental binding energiesE _b and two neutron separation energiesS _2n very well. The predicted neutron drip line nuclei are²⁸O,⁷²Ca,⁹⁸Ni,¹³⁶Zr,¹⁷⁶Sn, and²⁶⁶Pb. Halo and giant halo properties predicted in Ca isotopes withA>60 are investigated in detail through analysis of two neutron separation energies, nucleon density distributions, single particle energy levels, and the occupation probabilities of energy levels including continuum states. The spin-orbit splitting and the diffuseness of nuclear potential in these Ca isotopes, as well as the neighboring lighter isotopes in the drip line Ca region and find certain possibilities of giant halo nuclei in the Ne−Na−Mg drip line nuclei are also studied.     

Shell-model calculations for the zinc isotopes

Shell-model calculations for the zinc isotopes have been carried out with active particles distributed in the $\text{1}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{, 0}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{and}\text{1}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ orbits outside a closed “⁵⁶Ni” core. The effective Hamiltonian used was one obtained by Koops and Glaudemans from a fit to Ni and Cu level energies. An average absolute deviation of 0.19 MeV between the calculated and experimental ground-state binding energies is obtained for the A = 62?68 Zn isotopes. Good agreement is also found between most calculated and experimental excitation energies and spectroscopic factors for single-nucleon transfer for the low-lying levels in these nuclei. Experimentally known B(E2) values are generally well reproduced by the present model with effective charges of 1.0 ± 0.1 and 1.6 ± 0.2 for the neutron and proton, respectively. Magnetic dipole as well as Gamow-Teller transitions are not well accounted for by these calculations and seem to be sensitive to excitations of the ⁵⁶Ni core.     

Shell structure of even-even nickel isotopes containing twenty to forty neutrons

Shell parameters of even-even nickel isotopes involving twenty to forty neutrons are analyzed, and the results of this analysis are presented. A detailed comparison of the results obtained by calculating, on the basis of the mean-field model with the Koura-Yamada potential and the dispersive optical potential, single-particle energies of proton and neutron subshells with experimental data on the isotopes ^{56,58,60,62,64,68}Ni and with evaluated data on the neutron-deficient isotopes ^48,50,52,54Ni is performed.     

Structure of even-even beryllium isotopes studied by AMD+GCM method

The ground state properties and the properties of low-lying states of the even-even⁶Be-¹²Be beryllium isotopes are investigated using the extended version of the Antisymmetrized Molecular Dynamics Multi-Slater Determinant model. The theoretical method is found to be very useful to study ground state properties of various nuclei covering light unstable nuclei. Many experimental data can be successfully reproduced by the adopted approach. Binding energies, the energies of the 2 ₁ ⁺ states, electromagnetic transition strengths and quadrupole moments of proton and neutron distribution are calculated. This work is supported in part by Grant-in-Aid for Scientific Research (13740145) from the Ministry of Education, Science and Culture.     

Backbending of Dy isotopes described with the neutron-photon IBA plus two-quasiparticle model

The formalism of the neutron-photon interacting boson model, extended to include two-quasiparticle excitations, is used in a study of the high spin states of ^154,156,158Dy isotropes. Good agreement is obtained between the calculated energies and transition rates and the experimental results.