Relativistic Consistent Angular-Momentum Projected Shell-Model：Angular-Momentum Projection

The angular-momentum projection part of RECAPS is presented.Application of RECAPS to some deformed nuclei is also presented.

Relativistic Consistent Angular-Momentum Projected Shell-Model： Relativistic Mean Field

We develop a relativistic nuclear structure model, relativistic consistent angular-momentum projected shell-model (RECAPS), which combines the relativistic mean-field theory with the angular-momentum projection method. In this new model, nuclear ground-state properties are first calculated consistently using relativistic mean-field (RMF) theory. Then angular momentum projection method is used to project out states with good angular momentum from a few important configurations. By diagonalizing the hamiltonian, the energy levels and wave functions are obtained. This model is a new attempt for the understanding of nuclear structure of normal nuclei and for the prediction of nuclear properties of nuclei far from stability. In this paper, we will describe the treatment of the relativistic mean field. A computer code, RECAPS-RMF, is developed. It solves the relativistic mean field with axial-symmetric deformation in the spherical harmonic oscillator basis. Comparisons between our calculations and existing relativistic mean-field calculations are made to test the model. These include the ground-state properties of spherical nuclei 16O and 208Pb, the deformed nucleus 20Ne. Good agreement is obtained.

Structure of high spin state in proton-rich ^(74,76,78)Kr isotopes:A projected shell model description

The N≈Z nuclei in the mass A^80 region has been researched because of an abundance of nuclear structure phenomena.The projected shell model(PSM)was adopted to investigate the structure of high spin state in proton-rich 74,76,78Kr isotopes including yrast spectra,moment of inertia,electric quadrupole transitions and the behavior of single particle.The calculated results are in good agreement with available data and the shape coexistence in low-spin is also discussed.

On the structure of isomeric state in neutron-rich 108Zr: A projected shell model analysis

Inspired by the recent experimental identification of the new isomer with a half-life of （620±150） ns in the very neutron-rich nucleus 180SZr, we apply the projected shell model with axially-deformed bases to discuss possible shapes near the ground state and the nature of the isomer. The structure of the new isomer is investigated by restricting the calculation to prolate and oblate shapes. It is shown that the isomer can be understood as a K-isomer. Meanwhile, the calculation predicts more low-lying high-K configurations, which may be confirmed by future experiments,

Rotational structure of the odd-proton nuclide ^(171)Tm:A projected shell model study

Deformed odd-mass nuclei are ideal examples where the interplay between single-particle and collective degrees of freedom can be studied. Inspired by the recent experimental high-spin data in the odd-proton nuclide 171 Tm, we perform projected shell model(PSM) calculations to investigate structure of the ground band and other bands based on isomeric states. In addi- tion to the usual quadrupole-quadrupole force in the Hamiltonian, we employ the hexadecapole-hexadecapole(HH) interac- tion, in a self-consistent way with the hexadecapole deformation of the deformed basis. It is found that the known experi- mental data can be well described by the PSM calculation. The effect of the HH force on the quasiparticle isomeric states is discussed.

Systematic study of odd-mass^151-161Pm and^154,156Pm isotopes using projected shell model

Inspired by the availability of recent experimental as well as theoretical data on the energy levels of odd-mass^151-161Pm and odd-odd^154,156Pm,we applied the theoretical framework of the projected shell model to further understand the nuclear structure of these nuclei.The calculations closely reproduced the experimental data reported for the yrast bands of these isotopes by assuming an axial(prolate)deformation of^0.3.Other properties along the yrast line,such as transition energies and transition probabilities,have also been discussed.Band diagrams are plotted to understand their intrinsic multi-quasiparticle structure,which turn out to be dominated by 1-quasiparticle bands for the odd-mass Pm isotopes and 2-quasiparticle bands for the doubly-odd Pm isotopes under study.The present study not only confirms the recently reported experimental/theoretical data,but also extends the already available information on the energy levels and adds new information regarding the reduced transition probabilities.

Angular Momentum Projected Potential-Energy-Surface Calculation:Application to ^(178)Hf

An angular momentum projected potential-energy-surface （PES） calculation, which takes both rotational symmetry restoration and multi-quasiparticle excitation into account, is developed by using the macroscopic-microscopic model and the projected shell model （PSM）. Within this method, it may become possible to modify the excitation spectra which are influenced by shape-softness of nuclei, including high-K states. As our first example, this method is adopted to study the collective and multi-quasiparticle excitations of 178Hf~ and the results are in good agreement with the existing experimental data. In addition, as for the dominant structure of non- collective 6＋ bands, the conflict between experimental result and the previous PSM calculation is clarified.

Microscopic Study of Band Structures in^(98-102)Sr and^(100-104)Zr Isotopes

The properties of the high spin states of the neutron-rich 98-102Sr and 100-104Zr isotopes have been st udied using the projected shell model. In particular, the upbending phenomenon is investigated for these isotopes along the yrast line. The results show that the occurrence of upbending phenomenon is attributed to the band crossing between ground state band and 2-qp neutron band having configuration 2vh11/2[-3/2, 5/2], K = 1. Furthermore, the neutron two-quasi-particle structure of side bands in 98SR-102Zr is discussed in this paper.

Competition between collective oblate rotation and non-collective prolate K isomerism in neutron-rich tungsten isotopes

Recent experiments open up the possibility to investigate oblate rotation-aligned states and prolate high-K isomers in neutron-rich tungsten isotopes.In the present work,we perform the projected-shell-model calculations for A ～ 190 tungsten nuclei.The 190 W results are compared with experimental data.The observed 8 + isomer is assigned as a two-quasiproton K π = 8 + configuration.Low-lying high-K four-quasiparticle states are predicted.Of particular interest is the prediction of the K π = 20 + state in 190,192 W,which may form a long-lived spin trap.In competition with the prolate high-K states,rotational alignment leads to near-yrast collective oblate rotation.

Evolution of intrinsic nuclear structure in medium mass even-even Xenon isotopes from a microscopic perspective

In this study,the multi-quasiparticle triaxial projected shell model(TPSM)is applied to investigateγ-vibrational bands in transitional nuclei of 118-128Xe.We report that each triaxial intrinsic state has aγ-band built on it.The TPSM approach is evaluated by the comparison of TPSM results with available experimental data,which shows a satisfactory agreement.The energy ratios,B(E2)transition rates,and signature splitting of theγ-vibrational band are calculated.

Nuclear structure around ^(80)Zr

Recent years have witnessed intense activity concerning the study of nuclei with equal numbers of neutrons and protons （N = Z）. Exotic properties have been exhibited in the N = Z nuclei, especially in those with atomic masses around 80. In the present paper, the projected shell model（PSM）together with a relativistic Hartree-Bogoliubov （RHB） theory is used to study the nuclear structure near the N = Z line in the mass A ≈ 80 region. For three Zr isotopes 80,82,84Zr, the projected potential energy surfaces and ground state bands are calculated. It is shown that shape coexistence occurs in all of these nuclei. Moreover, we find that the residual neutron-proton interaction strongly affects the ground state band of 80Zr; however, it slightly modifies those of 82Zr and 84Zr.

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.

Mixing of two-quasineutron and two-quasiproton K~π=6^+ configurations in the vicinity of ^(174)Yb

In the framework of the projected shell model, we investigate the competition between the two-quasineutron and two-quasiproton K~π=6~＋ states in the ytterbium isotopes and N =104 isotones adjacent to ^（174）Yb. The ^（174）Yb results are compared with the experimental data.The K~π =6~＋ isomer observed in ^（174） Yb is assigned as an admixture of the ν7/2^-[514] ν5/2^-[512] and π7/2~＋ [404]π5/2~＋ [402] intrinsic structure, which explains the experimental ｜g K-g R ｜ value. Similar mixing would appear in ^（174） Yb, ^（176） Hf,and ^（178） W. The low-lying K~π=6~＋ states are also predicted in ^（170-178） Yb.