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.     

A≈110质量区奇A核形状演化研究

应用E-GOS（E-Gamma Over Spin）曲线方法研究了A≈110质量区奇A核结构随角动量增加的演化, 发现随着角动量的增加原子核的激发特性从振动逐渐演化为转动。 The E-GOS（E-Gamma Over Spin）curves were used to investigate the structure evolution in the odd A nuclei around A≈110 as a function of spin. The result shows that there is a clear transition from vibration to rotation while increasing spin.     

Structure analysis of ~(159)Sm and properties of odd-mass neutron-rich nuclei in mass-160 region

Recent fission experiment data provide interesting structure information for neutron-rich nuclei in the mass A ～ 160 region. We apply the projected shell model to study the strongly-deformed, neutron-rich Sm isotopes. We perform calculations for rotational bands up to spin I = 20 (29/2) for even-even (odd-neutron) Sm isotopes, and analyze the band structure of low-lying states with quasiparticle excitations. Emphasis is given to rotational bands based on one-quasiparticle (1-qp) configurations in the odd-ma...     

奇质量核的超越平均场玻色子费米子模型描述(英文)

对近年发展起来的一个基于核密度泛函理论和粒子核心耦合方案来计算中重质量奇A核谱性质的理论方法进行了评述。该方法首先在平均场层面通过选择合适的能量密度泛函和对力结构来自洽求解偶偶核心的势能曲面、球单粒子能级和奇粒子占有率,进一步将得到的结果作为微观输入来建立相互作用玻色子费米子模型哈密顿量,其中三个与粒子核心耦合强度相关的参数需要通过拟合一些特定奇质量核低激发谱数据来最终确定。通过对轴形变奇质量Eu同位素的低激发能谱和电磁跃迁几率的系统研究来说明该模型方法的有效性。另外,还讨论了该方法在描述轴形变奇质量核形状相变以及描述丰中子奇质量Ba同位素中八极关联方面的应用。A recently developed method for calculating spectroscopic properties of medium-mass and heavy atomic nuclei with an odd number of nucleons is reviewed, that is based on the framework of nuclear energy density functional theory and the particle-core coupling scheme. The deformation energy surface of the eveneven core, as well as the spherical single-particle energies and occupation probabilities of the odd particle(s), are obtained by a self-consistent mean-field calculation with the choice of the energy density functional and pairing properties. These quantities are then used as a microscopic input to build the interacting bosonfermion Hamiltonian. Only three strength parameters for the particle-core coupling are specifically adjusted to selected data for the low-lying states of a particular odd-mass nucleus. The method is illustrated in a systematic study of low-energy excitation spectra and electromagnetic transition rates of axially-deformed odd-mass Eu isotopes. Recent applications of the method, to the calculations of the signatures of shapes phase transitions in axially-deformed odd-mass nuclei, octupole correlations in neutron-rich odd-mass Ba isotopes, are discussed.     

Se同位素的形状共存

基于形变Woods Saxon势下的推转壳模型对Se同位素进行Total Routhian Surface (TRS) 计算。 结果表明, 原子核的形状随中子数变化很明显。 对66,72, 92, 94Se 基态TRS图进行分析, 发现缺中子同位素和中子滴线附近核素均存在扁椭球和长椭球的形状共存。 分别对72Se和94Se进行推转计算,长椭球和扁椭球形状在低推转频率下共存, 由于g9/2闯入轨道的影响, 随着推转频率的增加,扁椭球形变逐渐消失,长椭球形变带成为转晕带。 Nuclear shape change and shape coexistence in the Selenium isotopes have been investigated by Total Routhian Surface(TRS) calculations. It is found that nuclear shapes vary significantly with increasing neutron number. The TRS calculations for the ground states of 66, 72, 92, 94Se isotopes show that both neutron deficient and neutron dripline Selenium isotopes have oblate and prolate shape coexistence. The cranking shell model calculations for 72, 94Se give that prolate and oblate shape coexistence in low rotational frequency. However, oblate rotational bands disappear and prolate rotational bands become yrast bands with increasing rotational frequency, which is due to the intrusion of the g9/2 orbitals.     

B(E2) value of even-even ~(108-112)Pd isotopes by interacting boson model-1

This work studies the systematic reduced transition probabilities B(E2)↓,intrinsic quadrupole moments and deformation parameters of Pd isotopes with even neutrons from N=62 to 66.The downward reduced transition probabilities B(E2)↓from gamma transition 8+to 6+,6+to 4+,4+to 2+and 2+to 0+states of even-even108 112Pd isotopes were calculated by the Interacting Boson Model(IBM-1)and compared with the available previous experimental results.The ratio of the excitation energies of the first 4+and the first 2+excited states,R4/2,is also studied for the classification of symmetry of these nuclei.Furthermore we have studied systematically the transition rate R=B(E2:L+→(L 2)+)/B(E2:2+→0+)of some of the low-lying quadrupole collective states in comparison with the available experimental data.The associated quadrupole moments and deformation parameters have been calculated.The results of this calculation are in good agreement with the corresponding available experimental data.The108 112Pd isotopes show the O(6)symmetry.     

Rotational to vibrational evolution in some rotational-like nuclei

The excitation spectra of nuclei in the regions 150156Gd. Also we have shown the result of the nucleus ¹⁰²Ru which is given as an example of the reverse transition, i.e., vibration to rotation. The TRS plots reveal that, as the spin increases up the band, the former nucleus becomes slightly soft in γ and β direction, whereas the latter becomes rigid in γ direction.     

丰中子锶同位素的投影壳模型研究

利用考虑跨壳激发的投影壳模型（PSM）方法,研究了质子数Z=38、中子数N=63和64大形变丰中子101,102Sr同位素的结构性质。主要计算了转动谱、转动惯量和电磁跃迁性质等（如B（E2）和g因子）,并与相应的实验数据进行系统比较和相关的理论预言。结果表明,PSM可以利用理论计算的能带图解释101,102Sr同位素的转动惯量、电磁跃迁随自旋的变化,分析晕带的结构。PSM理论可以很好地再现实验结果,说明PSM方法及其采用的有效相互作用可以外推研究丰中子核区101,102Sr同位素的原子核结构。对于101,102Sr同位素,核子开始填布质子g_9/2和中子h_11/2轨道,通过更为仔细地分析能带图中来自质子g_9/2和中子h_11/2轨道对各转动带的组态成分的贡献,清晰地表明丰中子核结构性质对不同核子填布的依赖。Recently, we have carried out systematically studies on the structural properties of proton number Z=38, neutron number N=63 and 64 neutron-rich isotopes 101,102Sr by using the projected shell model (PSM) with consideration of cross shell excitation. The rotation spectra, the moment of inertia and the electromagnetic transition properties (such as B(E2) and g-factor) are calculated and compared with the corresponding experimental data in this paper. Furthermore, more high spin states are predicted in the calculation and expected to be confirmed experimentally. The results show that the PSM can not only well analyze the structural properties of yrast bands in 101,102Sr but also interpret the variation of the moment of inertia, electromagnetic transition with spins in terms with the theoretical band diagram. The good agreement with the experimental data suggests that the PSM with the adopted effective interactions can be generalized to study the nuclear structure of 101,102Sr isotopes in neutron-rich mass region. For 101,102Sr isotopes, the nucleons begin to fill proton g_9/2 and neutron h_11/2 orbital, the dependence of nuclear structure and properties on the different orbital occupies is described by carefully analyzing the contribution from proton g_9/2 and neutron h_11/2 orbital to the configuration of rotational bands in band diagram.     

B（E2） value of even-even ^108-112Pd isotopes by interacting boson model-1

This work studies the systematic reduced transition probabilities B（E2）↓, intrinsic quadrupole moments and deformation parameters of Pd isotopes with even neutrons from N =62 to 66. The downward reduced transition probabilities B（E2）↓from gamma transition 8^＋to 6^＋, 6^＋ to 4^＋, 4^＋ to 2^＋ and 2^＋ to 0＋states of even-even108 112Pd isotopes were calculated by the Interacting Boson Model（IBM-1） and compared with the available previous experimental results. The ratio of the excitation energies of the first 4＋and the first 2＋excited states, R4/2, is also studied for the classification of symmetry of these nuclei. Furthermore we have studied systematically the transition rate R = B（E2： L＋ →（L 2）＋）/B（E2 ： 2＋ →0＋） of some of the low-lying quadrupole collective states in comparison with the available experimental data. The associated quadrupole moments and deformation parameters have been calculated. The results of this calculation are in good agreement with the corresponding available experimental data. The108 112Pd isotopes show the O（6） symmetry.     

平均场加邻近轨道对力模型描述N=94同中异质素性质

利用严格可解的Nilsson平均场加邻近轨道对力模型,在区分质子和中子情况下,研究了大形变核的性质,主要计算了中子数为N=94的同中异质素的结合能、奇偶能差和转动惯量,并与相应的实验值进行了系统比较,结果表明此模型可以合理描述这些性质,正确反映原子核奇偶性质的变化规律。然后以偶偶核160Dy为例,研究了基态中各角动量J=0,1,...,12价核子对的占有率。结果表明,偶角动量占有率远高于奇角动量占有率,其中S,D,G价核子对各组份在基态波函数中是主要的。The Nilsson mean-field plus the nearest orbit pairing model for deformed nuclei is applied to investigate systematically the properties of the N=94 nuclei,employing both proton-proton and neutron-neutron pairing interactions.The binding energies,even-odd mass differences,moments of inertia are calculated and compared with the corresponding experimental data.The results show that this model can reasonably describe these properties.Further,the ground-state occupation probabilities of valence nucleon pairs with angular momentum J=0,1,...,12 for even-even 160Dy are calculated,and the results show that it is much higher for the even angular momenta than the odd angular momenta,and the S,D,G components in the ground-state wave function are dominant.     

Analysis of the scattering of 46 MeV protons from Be and C

An analysis is made of the measurements of the elastic and inelastic scattering of 46 MeV protons by ³Be and ¹²C. The optical and collective models are used. There is considerable ambiguity in the optical parameters, and it was not found possible to obtain good fits to cross sections and polarizations simultaneously. Large quadrupole deformations were found for both ¹²C (β₂ ≈ 0.6) and ⁹Be(β₂ ≈ 1). The inelastic scattering from ¹²C agrees best with deformation of both real and imaginary parts of the optical potential, while ⁹Be shows a preference for real coupling. The 14.1 MeV level in ¹²C is interpreted as the 4⁺ rotational state, while the angular distribution for the 7.6 MeV 0⁺ level is well described by double quadrupole excitation via the lowest 2⁺. Interpretations are suggested for other inelastic transitions, including the excitation of spin and isospin oscillations.     

Criteria of the Spin Assignment of Rotational Band

Based on the very general properties of the rotational band of axially symmetric nucleus, some rules of the I variation of the kinematic and dynamic moments of inertia are obtained, which may serve as the effective criteria of the spin assignment of rotational band. Extensive analysis of large amount of ro tational bands (below bandcrossing) of normally deformed eveneven nuclei whose spins were established shows that these rules do hold without exception. The spins of the yrast superdeformed bands of even-even nuclei in the actinide region (fission isomeric bands), and in the A～190, 150 regions are analyzed also. The spin of the lowest observed level of the yrast superdeformed band in ¹⁵²Dy is determined to be I₀ = 26, rather than I₀ = 22 or 24.     

奇A核Pd同位素中h_(11/2)入侵轨道的形状驱动效应研究

过渡区原子核的形变与准粒子占据的轨道密切相关。采用推转壳模型首次系统性地研究了奇A核~(99)Pd,~(101)Pd和~(103)Pd原子核中h_(11/2)轨道对核芯的形状驱动效应,基于Total-Routhian-Surface(TRS)方法的计算结果表明,当过渡区原子核~(99)Pd,~(101)Pd和~(103)Pd中的准粒子开始占据h_(11/2)入侵轨道时将会使原子核产生稳定的四极形变。另外,对A≈210质量区近滴线核的高自旋态研究现状及今后进一步的工作也进行了概述。     

Rotational Property of~(249)Cm in Particle-Triaxial-Rotor Model

We study the rotational energy spectrum and deformation feature of very heavy nucleus 249Cm in the particle-triaxial-rotor model with variable moment of inertia.Such a nucleus is the unique one involving both multiband structure and high spin states and locating very near the superheavy region.By calculating the energy spectrum,we determine the configurations and quadrupole and triaxial deformation parameters β and γ of the nucleus.The calculated results indicate that the high spin band of 249Cm is built upon the ν[620] 12+configuration with deformation parameters β = 0.296 and γ = 7.5 and the bands based on the ν[622] 32+,ν[613] 72+,ν[750] 12 configuration respectively are also the ones with quite large axial deformation but small triaxial deformation.     

Microscopic Study of Band Structures in98-102Sr and 100-104Zr Isotopes

The properties of the high spin states of the neutron-rich ^98-102Sr and ^100-104Zr isotopes have been studied 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 2νh_{11 / 2}[-3/2, 5/2], K=1. Furthermore, the neutron two-quasi-particle structure of side bands in ⁹⁸Sr and ¹⁰²Zr is discussed in this paper.     

Lifetime measurements in Pt and the shape coexistence picture

Lifetimes for levels in the yrast band of ¹⁸⁴Pt have been measured up to spin 16⁺ using the recoil distance technique. The B(E2) values exhibit a marked increase in going from spin 2 to 10, consistent with a proposal that two bands of different deformations are mixing at low spin. This provides further support for shape coexistence occuring at low excitation energies in this region.     

Nuclear structure studies at Saha Institute of Nuclear Pysics using gamma detector arrays

In-beam gamma-ray spectroscopy, carried out at the Saha Institute of Nuclear Physics in the recent past, using heavy-ion projectiles from the pelletron accelerator centres in the country and multi-detector arrays have yielded significant data on the structure of a large number of nuclei spanning different mass regions. The experiments included the study of two-fold γγ-coincidence events for establishing decay schemes, directional correlation of oriented nuclei (DCO) for help in spin assignments and Doppler shift attenuation for lifetime information. The studies have led to the observation of rotational sequences of states in nuclei near closed shell in the mass A=110 region, vibrational spectra in nuclei with A ∼ 60, interplay between single-particle and collective modes of excitation in the doubly-odd bromine isotopes, decoupled bands with large quadrupole deformation in ⁷⁷Br, shape transition with rotational frequency within a band in ¹³⁵Pm and octupole collectivity in ¹⁵³Eu. Particle-rotor-model and cranked-shell-model calculations have been carried out to provide an understanding of the underlying nuclear structure.     

Ground-State Bands of Fm and No Isotopes in Cluster Model

We investigate the ground-state rotational bands of nuclei with Z 〉 100 using cluster model proposed by Buck et al. [Phys. Rev. Left. 94 （2005） 202501]. The core-duster decomposition of each nucleus is determined by the corresponding electric quadrupole transition strength B（E2 ： 2^＋ → 0^＋）. The theoretical spectra of fermium and nobelium isotopes are compared with available experimental data. Good agreement between model and data is obtained.