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.     

Candidate chiral nuclei in bromine isotopes based on triaxial relativistic mean field theory

Following the observation of candidate chiral doublet bands in ~(78,80)Br, triaxial deformations with corresponding configurations in odd-odd bromine isotopes have been investigated using adiabatic and configuration-fixed constrained triaxial relativistic-meanfield calculations with an aim of finding the boundary of chirality in the chain of Br isotopes. Several minima with triaxial deformation and the proper particle-hole configuration were obtained in ~(74,76,78,80,82)Br, where the chiral doublet bands have the possibility of occurrence. Furthermore, the possible existence of multiple chiral doublet(MχD) bands is demonstrated in ~(74,76,78,80,82)Br.Experiments to explore the chirality and MχD properties of Br isotopes are conducted to verify the predictions.     

Possible Candidates for Chirality in the Odd-Odd As Isotopes

The deformations and the corresponding configurations of the odd-odd As isotopes are investigated using the adiabatic and configuration-fixed constrained triaxial relativistic mean field(RMF) theory.Energy minima with triaxial deformations and high-j particle-hole configurations are obtained in ~(72,74,76,78,80)As,where the chiral doublet bands are possible to appear.The existence of multiple chiral doublet(M_χD) is demonstrated in ~(74,76,78)As.Based on the calculated single-particle levels,we also find possible coexistence of chiral and pseudospin symmetries in the odd-odd As isotopes.     

Search for the chiral Band in the N=71 Odd—odd Nucleus ^126Cs

High-spin states in ^126Cs are studied via the ^116Cd(^14N,4n) reaction at a beam energy of 65MeV.The sideband of the πvh11/2 yrast band,a ΔI=2 band known from previous study,is developed into a ΔI=1 coupled structure at low spins.This sideband is assigned to be built on the same configuration as the yrast band according to the measured ratios of directional correlation of orientation and observed alignment properties.On the basis of comparisons with the previously proposed chiral doublet bands for ^128,130Cs,the observed two πh11/2 vh11/2 bands are proposed to be candidates for chiral doublet bands in ^126Cs.     

Proposed Chiral Doublet Bands in ^98Tc

High spin states in odd-odd ^98 Tc nuclei are studied by in-beam γ-ray spectroscopy with the ^96 Zr（^6Li, 412） fusionevaporation reaction at a beam energy of 35MeV. The previous level scheme is updated. A band based on 1090.7keV is expanded, and another band based on 1920.6 keV is newly identified. The observed two negative parity bands in ^98 Tc are proposed to be a pair of chiral doublet bands with the configuration πg9/2 vh11/2. The evidence supporting the assignment of the chiral doublet bands is discussed. Signature splitting and signature inversion are observed in the πg9/2 vh11/2 band in ^98Tc.     

Examining the Chiral Geometry in l04Rh and l06Rh

The criteria for chiral doublet bands based on one particle and one hole coupled to a triaxial rotor have been summarized. Two representative cases in A - 100 odd-odd nuclei, nearly degenerate △I = 1 doublet bands in 104Rh and 106Rh, are checked against these chiral criteria. It is shown that 106Rh possesses better chiral geometry than 104Rh, although the energy near degeneracy is achieved in 104Rh in comparison with the constant energy separation of doublet bands in 106Rh.     

Chiral doublet bands and energy-level crossing

Different definitions for chiral doublet bands based on excitation energies, B(E2) and B(M1) respectively are discussed in the triaxial particle rotor model. For the ideal chiral geometry, the selection rules of the electromagnetic transitions in different band definitions are illustrated. It is also shown that the energy-level crossings between chiral doublet bands may occur.     

Chiral doublet bands and energy-level crossing

Different definitions for chiral doublet bands based on excitation energies, B(E2) and B(M1) respectively are discussed in the triaxial particle rotor model. For the ideal chiral geometry, the selection rules of the electromagnetic transitions in different band definitions are illustrated. It is also shown that the energy-level crossings between chiral doublet bands may occur.     

πg9/2(⊕)vh11/2 doublet bands in A～100 mass region

Using the model with one particle and one hole coupled with a triaxial rotor, the πg(-1)(9/2)(⊕)vh11/2 doublet bands in the A ～ 100 mass region are studied, and compared with the πh11/2(⊕)vh(-1)(11/2) doublet bands.It is found that the calculated results for the configuration of πg(-1)(9/2)(⊕)vh11/2 are very similar the results for a pure h11/2 proton particle and a neutron quasiparticle with λn =ε5. After including the pair correlation, the model describes the candidate chiral doublet bands in 106Rh successfully, which supports the interpretation of chirality geometry.     

Description of the candidate chiral doublet bands in 98Tc

The candidate chiral doublet bands in ⁹⁸Tc with configuration πg_9/2 × νh_11/2 are studied theoretically for the first time via the triaxial particle rotor model. The main properties of the doublet bands including the energy spectra and electromagnetic transitions are calculated for different triaxiality parameter γ, and the data in ⁹⁸Tc can be well described by the calculations with γ=38°. Based on the analysis of angular momentum components, it is found that the chiral rotational geometry in ⁹⁸Tc deviates from the ideal chiral picture.     

Band Interaction between Chiral Doublet Bands

Band interaction between the chiral doublet bands based on πh11/2？νh？111/2 configuration is investigated in the particle rotor model with different triaxial deformation γ. The variation of chiral partner states with γ values is understood qualitatively based on the basic picture of two interaction levels, which is confirmed further by the calculated overlap integral of wave functions at different γ values. It is found that the interaction strengths of chiral partner states are obviously different for odd spins and even ones.     

πg9/2νh11/2 doublet bands in A～100 mass region

Using the model with one particle and one hole coupled with a triaxial rotor, the πg9/2/1/2νh11/2 doublet bands in the A～100 mass region are studied, and compared with the πg9/2/1/2νh11/2 doublet bands. It is found that the calculated results for the configuration of πg9/2/1/2νh11/2 are very similar the results for a pure h11/2 proton particle and a neutron quasiparticle with λn = ε5. After including the pair correlation, the model describes the candidate chiral doublet bands in 106Rh successfully, which supports the interpretation of chirality geometry.     

Chiral doublet bands in odd-odd nuclei

The criteria for chiral doublet bands based on one particle and one hole coupled to a triaxial rotor have been summarized. Candidate chiral doublet bands in A~100 and 130 odd-odd nuclei were checked against these chiral criteria. Two representative cases, nearly degenerate ΔI =1 doublet bands in ¹²⁶Cs and ¹⁰⁶Rh were investigated in the two quasiparticles coupled with a triaxial rotor model. After including the pairing correlation, good agreement has been obtained between the calculated results and the data available, which supports the interpretation of observed doublet bands as chiral bands.     

Electromagnetic Transition Strengths and New Insight into the Chirality in ^106Ag

Excited states in ^106Ag are populated through the heavy-ion fusion evaporation reaction ^100Mo（ll B,5n）^106Ag at a beam energy of 60MeV. Lifetimes are measured for transitions of the two negative-parity rotational bands in the nucleus ^106Ag. The reduced transition probabilities show a great difference between the two bands. The staggering of the B（M1） and B（M1）/B（E2） values with spin are not observed. The bands are identified to be built on two distinct quasiparticle configurations. These results are contrary to an earlier suggestion that the pair of bands in ^106Ag are chiral doublet bands.     

Gamma Vibrational Bands and Chiral Doublet Bands in A≈100 Neutron-rich Nuclei

The level structures of neutron-rich ~(105)Mo,~(106)Mo,~(108)Mo and 110Ru nuclei in A≈100 region have been carefully investigated by coincidence measurements of the prompt γ-rays populated in the spontaneous fission of ~(252)Cf with the Gammasphere detector array.In 105Mo,one-phonon K =9/2 and two-phonon K=13/2 γ-vibrational bands have been identified.In ~(108)Mo,one-phonon γ-vibrational band is expanded and two-phonon γ-vibrational band has been identified.Two similar sets of bands in ~(106)Mo and ~(110)Ru are observed to high spins,which have been proposed as the soft chiral γ-vibrational bands.The characteristics for these γ-vibrational bands and chiral doublet bands have been discussed.     

Description of Chiral Doublet Bands in Odd-Odd Cs Isotopes

Properties of the chair doublet bands of the odd-odd Cs isotopes built on the πh11/2× vh11/2 configuration are investigated systematically within the supersymmetry scheme including many-body interactions and possessing the SO（5）（or SU（5）） symmetry on the rotational symmetry. Quantitatively good results of the energy spectra, the energy staggering parameter as a function of the spin are obtained. The calculation shows that the stronger competition between the pairing and anti-pairing effects and the SU（3） symmetry broking more seriously exist in the stable chiral structure.     

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.     

Nuclear Current and Magnetic Rotation

The magnetic rotational bands based on the configuration πh11/2^2 vh11/2^-2 in ^142Gd are investigated with the newly developed tilted axis cranking relativistic mean field （RMF） theory with and without nuclear current. The effect of the nuclear current is discussed by comparing the total Routhians, single particle levels, electromagnetic transition probabilities B（M1） and B（E2） in self-consistent tilted axis cranking RMF caIculation with those obtained without the nuclear current. The nuclear currents are found to play an important role in the magnetic rotation of nuclei.     

Band Structures of the Nucleus 129Cs

High-spin states in ^129Cs are populated via the ^122Sn （^11B, 4n） reaction at beam energies of 55 and 60MeV. Two additional bands are placed in the level scheme and the previously known bands are extended to higher spins. The results are compared to the cranked shell model calculations and to the systematics of the adjacent Cs isotpoes. One of the new bands is interpreted as the 7-vibrational band built on the πh11/2 orbital. The possible configuration for another new band is discussed. Upbend caused by （Vh11/2）^2 alignment is observed both in the favored and unfavored sequences of the πh11/2 configuration. The band based on the πgτ/2 configuration at low spins forks around spin 17//2, and the two different S-bands are attributed to （Vh11/2）^2 and （πh11/2）^2 rotational alignments, respectively.