Systematic Properties of the 1／2[660]^i13／2 Bands in Odd-A Au Nuclei

A standard in-beam γ-spectroscopy experiment for^179 Au has been performed via the ^149Sm (^35Cl, 5n) reaction at beam energies of 164-180 MeV. Based on the analysis of the experimental results, a rotational band built on 1/2[660](π^i13/2)proton intruder orbital is established for^179 Au for the first time. Systematic properties of the 1/2[660](π^i13/2) band in odd-A Au nuclei are discussed,and the evolution of bandhead energy and deformation with changing neutron number are revealed.     

Theoretical Study on Negative Parity States of^（191,193,195,197） Au in Particle Triaxial-Rotor Model

By taking the particle triaxial-rotor model with variable moment of inertia, we investigate the energy spectra, the deformation and the single particle configuration of the negative-parity states in nuclei^（191,193,194,197） Au systemically. The calculated energy spectra agree well with experimental data. The obtained results indicate that the negative-parity states in^（191,193,195,197）Au originate from the proton-hole h11/2 configuration coupled to a triaxial oblate Hg core. Meanwhile the main single particle configuration of the bands 1, 2 and 3 are identified to be [5h11/2 1/2） （α=-1/2）, [5h11/2 1/2） （α = 1/2） and 15h9/2 7/2）, respectively.     

Properties of the πh_(9/2)  νi_(13/2) band in odd-odd ~(188)Au

A new rotational band has been identified and assigned to 188Au for the first time using the 173Yb(19F,4nγ) reaction at the beam energies of 86 and 90 MeV. This band is proposed to be built on the πh9/2  νi13/2 configuration by comparing the band properties with known bands in neighboring nuclei. The prolate-to-oblate shape transition through triaxial shape has been proposed to occur around 188Au for the πh9/2  νi13/2 bands in odd-odd Au isotopes on the basis of total Routhian surface (TRS) calculations.     

Influence of Traxiality on the Signature Inversion in Odd-Odd Nuclei

The nature of signature inversion in the πg/2vh11/2 bands of odd-odd^98.102Rh nuclei is studied. Calculations are performed by using a triaxial rotor plus two-quasiparticle model and are compared with the experimentally observed signature inversions. The calculations reproduce well the observations and suggest that, in these bands, the signature inversion can be interpreted mainly as a competition between the Coriolis and the proton-neutron residual interactions in low K space. The triaxiality applied in the Hamiltonian enlarges the amplitudes of high spin signature zigzags at small triaxial deformation and might push the signature inversion point to higher spin at large triaxial deformation.     

Theoretical Calculation of Rotational Bands of ^179Pt in the Particle-Triaxial-Rotor Model

Theoretical calculations have been performed for nucleus ^179Pt in the particle-triaxial-rotor model with variable moment of inertia. The obtained energy spectrum agrees with the experimental data quite well. The calculated results indicate that the bands 1/2^- and 7/2^ are triaxial deformation bands and originate mainly from the v[521]1/2^- and v[633]7/2^ configurations respectively.     

Chiral geometry in multiple chiral doublet bands

The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with πh_(11)/2γh_(11/2)~(-1).The energy spectra,electromagnetic transition probabilities B(M1) and B(E2),angular momenta,and K-distributions are studied.It is demonstrated that the chirality still remains not only in the yrast and yrare bands,but also in the two higher excited bands whenγ deviates from 30°.The chiral geometry relies significantly on γ,and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands.     

A≈100和130核区手征双重带的描述

利用三轴形变的粒子 转子模型讨论了A≈100和A≈130核区手征双重带.基于粒子空穴组态πh11/2 νh-111/2的计算很好地再现了A≈130核区N=75同中子素的手征双重带实验能谱.通过分析基于组态πg9/2 νg-19/2的约化跃迁几率B(E2)和B(M1)研究A≈100核区可能的手征双重带. The Chiral doublets for nuclei in A≈100 and 130 regions have been studied with the particle-rotor model. The experimental spectra of chiral partner bands for four N=75 isotones in A≈region have been well reproduced by the calculation with the configuration πh_(11/2)νh~(-1)_(11/2). The possible chiral doublets in A≈100 region have been predicted by the particle-rotor model (PRM) with the configuration πg_(9/2) νg~(-1)_(9/2) based on the analysis of the B(M1) and B(E2) transition probabilities.     

Octupole deformation for Ba isotopes in a reflection-asymmetric relativistic mean-field approach

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.     

Revisiting the island of hexadecapoledeformation nuclei in the A≈150 mass region: focusing on the model application to nuclear shapes and masses

Based on the potential-energy-surface calculation, the impact of different deformation degrees of freedom on a single-particle structure and binding energies in nuclei around ¹⁵²Nd, located on one of the hexadecapole-deformation islands, is analyzed in a multi-dimensional deformation space. Various energy maps, curves and tables are presented to indicate nuclear properties. The calculated equilibrium deformations and binding energies with different potential parameters are compared wi...     

Reflection-Asymmetric Shell Model Description of the Neutron-Rich^142，145Ba Nuclei

The reflection asymmetric shell model has been applied to describe the octupole deformed bands in neutron-rich even-even ^142Ba and odd-N^145Ba nuclei. The alternating parity bands of ^142Ba and the simplex s = -i bands of^145Ba are calculated and compared with the available experimental data. The calculated results are in good agreement with the experimental data. The spin and parity assignments of ground-state of^145Ba are discussed.The results show that the present work is a useful attempt to further explore the nuclear reflection asymmetry in neutron rich region.     

New multi-phonon gamma vibrational bands in A～110 neutron-rich nuclei

The high spin states of neutron-rich 103Nb, 107Tc and 109Tc nuclei in A~110 region have been investigated by measuring prompt γ-γ-γ coincident measurements populated with the spontaneous fission of 252Cf with the Gammasphere detector array. In 103Nb, one-phonon K = 9/2 and two-phonon K = 13/2 γ-vibrational bands have been identified. In 107Tc and 109Tc, one-phonon K = 11/2 and two-phonon K = 15/2 γ-vibrational bands, in which the zero-phonon bands are based on K=7/2 excited states, have also been identified...     

Isospin and F-spin symmetry structure in low-lying levels of 48，50Cr isotopes

The low-energy level structure and electromagnetic transitions of ^48.50Cr nuclei have been studied using the interacting boson model with isospin (IBM-3). A sequence of isospin excitation bands with isospin T = Tz, Tz 1and Tz 2 has been assigned, and compared with available data. According to this study, the 2^3 and 2^2 states are the lowest mixed symmetry states in ^48Cr and ^50Cr, respectively. In particular, the present calculations suggest that a combination of isospin and F-spin excitation can explain the structure in these nuclei. The transition probabilities between the levels are analysed in terms of isoscalar and isovector decompositions which reveal the detailed nature of the energy levels. The results obtained are in good agreement with recent experimental data.     

Investigation of the high-spin rotational properties of the proton emitter ~(113)Cs using a particle-number conserving method

The recently observed two high-spin rotational bands in the proton emitter ~(113)Cs are investigated using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the Pauli blocking effects are taken into account exactly. By using the configuration assignments of band 1 [π3/2~+[422](g_(7/2)), α =-1/2] and band 2 [π1/2~+[420](d_(5/2)), α=1/2], the experimental moments of inertia and quasiparticle alignments can be reproduced much better by the present calculations than those using the configuration assginment of π1/2~-[550](h_(11/2)), which in turn may support these configuration assignments. Furthermore, by analyzing the occupation probability nμ of each cranked Nilsson level near the Fermi surface and the contribution of each orbital to the angular momentum alignments, the backbending mechanism of these two bands is also investigated.     

High-K multi-particle bands and pairing reduction in 254No

The multi-particle states and rotational properties of the two-particle bands in 254No are investigated by the cranked shell model with pairing correlations treated by the particle number conserving method.The rotational bands on top of the two-particle K^π=3^+,8^− and 10^+ states and the pairing reduction are studied theoretically in 254No for the first time.The experimental excitation energies and moments of inertia of the multi-particle states are reproduced well by the calculations.Better agreement with the data is achieved by including the high-order deformation ε6,which leads to enlarged Z=100 and N=152 deformed shell gaps.An increase of J¹ in these two-particle bands compared with the ground state band is attributed to the pairing reduction due to the Pauli blocking effect.     

Octupole deformation for Ba isotopes in a reflection-asymmetric relativistic mean-field approach

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.     

Possible shape coexistence in Ne isotopes and the impurity effect of Λ hyperon

The possible shape coexistence in even-even Ne isotopes and the impurity effects of the sΛand pΛ hyperons are explored employing the multidimensionally constrained relativistic-mean-field(MDC-RMF) model with the PK1 parameter set for the N N interaction and PK1-Y1 for the ΛN interaction. The quadrupole deformation potential energy surfaces(PESs), nuclear deformations, nuclear radii, binding energies, and density distributions of the hypernuclei and core nuclei are examined. The possible shape coexistence in ~(24,26,28)Ne is predicted with small energy differences of 140, 336, and 128 keV, respectively, between the two local energy minima. Different impurity effects of the sΛand pΛ hyperons are revealed. The sΛ hyperon exhibits clear shrinkage effects, which reduce the nuclear size and facilitate a spherical nuclear shape. The prolate pΛhyperon on the 1/2~-[110] orbital renders the nuclear shape more prolate, while the oblate pΛ hyperon on the 3/2~-[101] or 1/2~-[101] orbital renders the nuclei more oblate. Moreover, the Λ hyperon can increase the probabilities of the shape coexistence by reducing the energy differences between the two local energy minima, although the shape coexistence may disappear owing to the vanishment of one energy minimum on the flat energy surface.     

Ground State Properties of New Element Z=113 and Its Alpha Decay Chain

We investigate the ground state properties of the new element ^278 113 and of the α-decay chain with different models, where the new element Z=113 has been produced at RIKEN in Japan by cold-fusion reaction [Morita et al. J. Phys. Soc. Jpn. 73 (2004) 2593]. The experimental decay energies are reproduced by the deformed relativistic mean-field model, by the Skyrme-Hartree-Fock (SHF) model, and by the macroscopic-microscopic model.Theoretical half-lives also reasonably agree with the data. Calculations further show that prolate deformation is important for the ground states of the nuclei in the α-decay chain of ^278 113. The common points and differences among different models are compared and discussed.     

Rotational properties of the odd-Z transfermium nucleus 255Lr by a particle-number-conserving method in the cranked shell model

Experimentally observed ground state band based on the 1/2-[521] Nilsson state and the first exited band based on the 7/2-[514]Nilsson state of the odd-Z nucleus ~(255)Lr are studied by the cranked shell model(CSM) with the paring correlations treated by the particle-number-conserving(PNC) method. This is the first time the detailed theoretical investigations are performed on these rotational bands. Both experimental kinematic and dynamic moments of inertia(J~(1)and J~(2)) versus rotational frequency are reproduced quite well by the PNC-CSM calculations. By comparing the theoretical kinematic moment of inertia J~(1) with the experimental ones extracted from different spin assignments, the spin 17/2~-→13/2~- is assigned to the lowest-lying 196.6(5) ke V transition of the 1/2~-[521] band, and 15/2~-→11/2~- to the 189(1) ke V transition of the 7/2~-[514] band, respectively. The proton N = 7 major shell is included in the calculations. The intruder of the high- j low-? 1 j_((15)/2)(1/2~-[770]) orbital at the high spin leads to band-crossings at ω≈0.20( ω≈0.25) Me V for the 7/2~-[514] α =-1/2(α = +1/2) band, and at ω≈0.175 Me V for the1/2~-[521] α =-1/2 band, respectively. Further investigations show that the band-crossing frequencies are quadrupole deformation dependent.     

Structure of the Semi—decoupled π 1／2[411] Band in Odd Proton Nucleus ^169Ta

High spin states of the odd proton-nucleus ^169Ta have been populated in the reaction ^155Gd(^19F,5n) with beam energies of 97MeV,Rotational band based on d3/2 proton 1/2[411]Nilsson state has been pushed up to 39/2^ in the α=1/2 decay sequence.Its signature partner,the α=-1/2 decay sequence with four link transitions has been established and 1/2[411] band in ^169Ta was reassigned to be a semi-decoupled band.The systematics of the signature splitting in the K=1/2 bands in the rear-earth region and the accidental degeneracy conclusion given by the angular projection shell model were discussed.     

Investigation of Exotic Structure of the Largely Deformed Nucleus ^23A1 in the Relativistic-Mean-Field Model

A candidate for proton halo nucleus ^23A1 is investigated based on the constrained calculations in the framework of the de[ormed relativistic mean tield (RMF) model with the NL075 parameter set. It is shown by the constrained calculations that the ground state of ^23A1 has a large deformation that corresponds to the prolate shape. With that large deformation, the non-constrained RMF calculation predicts that there appears an inversion between the 2s1/2 [211] and ld5/2 [202] shells. The valence proton of ^23A] is weakly bound and occupies 2s1/2 [211] and ld5/2 [202] with the weights of 56% and 29%, respectively. The calculated RMS radius for matter is in agreement with the experimental one. It is also predicted that the difference between the proton RMS radius and the neutron one is very large, This suggests that there exists a proton hMo in ^23Al.