High spin states in neutron-rich ~(106)Tc nucleus

The high spin states of the neutron-rich odd-odd 106Tc nucleus have been reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. A previously known collective band is confirmed and expanded, and a new collective band is newly identified. Several levels in previous report in 106Tc are reexamined and they belong to the members of a band in 107Tc. The total Routhian surface (TRS) calculations show that the 106Tc has triaxial shape. The spins and parities as well as the configurations f...     

Triaxial shape in 129Ce

The high spin states of ¹²⁹Ce have been populated via heavy-ion fusion evaporation reaction ⁹⁶Mo (³⁷Cl, 1p3n) ¹²⁹Ce. The comparison between the signature- and B(M1)-staggering defined by Hagemann and Hamamoto have been showed in the negative-parity band of ¹²⁹Ce. The lifetimes and quadrupole moments Q_t of the high spin states of ¹²⁹Ce have been extracted from the line shape analyses using Doppler shift attenuation method (DSAM). The deformation parameters extracted through the solution of equations for quadrupole transition moments Q_t and collective moments of inertia J_RR.     

146Ce核的八级形变带和准γ带

通过测量²⁵²Cf自发裂变所产生的瞬发γ射线, 对¹⁴⁶Ce核的高自旋结构进行了重新研究, 结果更新了以前报道的能级纲图, 把八级形变集体带扩展到更高的自旋, 并且重新构建了可能的准γ带结构. 此外, 用反射不对称壳模型(RASM)对¹⁴⁶Ce核的八级形变带进行了计算, 低自旋处的计算结果与实验数据符合得很好.     

Lifetimes of High Spin States in an Odd-Proton Nucleus 129Cs

Lifetimes of high spin states in 129Cs axe measured using the Doppler shift attenuation method. The high spin states of 129 Cs axe populated following the fusion evaporation reaction 124 Sn（UB, 6n）129 Cs at a beam energy of 65 MeV. The reduced transition probabilities B（E2） and the transition quadrupole moments Qt in the negativeand positive-paxity bands are deduced. The experimental results indicate that the Qt values of the negative parity band are smaller than those of the positive parity bands, probably due to different γ-deformation driving effects of different proton orbitals. The Qt values exhibit a considerable increase near the band crossing region in these bands. This behavior demonstrates that nuclear shape changing results from the neutron or proton alignments. The signature splitting of the πh11/2 and πg7/2 bands shows the opposite changing trend after backbending due to the h11~2 neutron and h11/2 proton alignments, respectively.     

Shape evolution and test of the critical-point symmetry X(5) in 176Os

The lifetimes of excited states in the yrast band of ¹⁷⁶Os have been measured up to I=20h level using the Doppler shift attenuation method. The high-spin states of ¹⁷⁶Os were populated via fusion evaporation reaction ¹⁵²Sm(²⁸Si, 4n)¹⁷⁶Os at a beam energy of 140 MeV. The results support an X(5) structure for ¹⁷⁶Os at low spin. This structure disappears at high spin and shows a symmetry rotor character. The shape change of ¹⁷⁶Os is similar to that of ¹⁷⁸Os.     

奇A 核的多声子γ振动带实验研究进展

对于近年来清华大学与美国合作研究组在原子核结构实验研究中有关奇A 核的多声子 振动带方面的进展进行了评述。研究人员通过有效的国际合作,识别了质量数A = 100 丰中子核区的奇A核103Nb,105Mo,107Tc 和109Tc中的两声子 振动带,这是迄今为止国际上在奇A 核的结构研究中发现的仅有的4 例这样的结构。对于实验方法、研究结果以及这些多声子 振动带的特性进行了评述,并对目前在多声子带其他方面的研究及今后进一步的工作进行了概述。The experimental research on multi-phonon γ-vibrational bands in odd-A nuclei by our international collaboration has been reviewed. The two phonon -vibrational bands in 103Nb, 105Mo, 107Tc and 109Tc in the A = 100 neutron-rich nuclear region were identified, which are the only four such bands discovered in nuclear structure studies until now. The experimental methods and results are summarized, and the characteristics for these band structures are discussed. The other aspects for our research on the multi-phonon vibrational bands as well as our future research work are also briefly reviewed.     

Search for chiral bands in A~110 neutron-rich nuclei

High spin states in A~110 neutron-rich ¹⁰⁶Mo, ¹¹⁰Ru and ¹¹²Ru nuclei have been reinvestigated by measuring the prompt γ-rays from the spontaneous fission of ²⁵²Cf. Two similar sets of bands are observed to high spins in each of three nuclei. Through analyzing of characters of the band structures, the chiral doublet bands are suggested in ¹⁰⁶Mo, ¹¹⁰Ru and ¹¹²Ru.     

Observation of a new rotational band in 104Nb nucleus

The high spin states in neutron-rich ¹⁰⁴Nb have been investigated from study of prompt γ-rays in spontaneous fission of ²⁵²Cf with the Gammasphere detector array. A new rotational band has been identified for the first time. This band is proposed as a semi-decoupled band based on the configuration π5/2^－[303]⊙ν1/2^－[541].     

134Ba核的高激发态能级结构研究

在中国原子能科学研究院H-13串列加速器上, 通过重离子核反应¹³⁰Te(⁹Be,5n)与在束γ谱的实验技术, 对A=130缺中子核区的¹³⁴Ba核的高自旋态进行了研究, 建立了¹³⁴Ba核的新的能级纲图, 最高自旋态扩展到20h. 除验证了以前报道的大部分能级与跃迁外, 将基带的能级扩展到10⁺, 同时发现了基于10⁺同质异能态以上的众多的能级与跃迁. 对实验结果的系统学分析表明, 10⁺同质异能态为yrast陷阱, 起源于两中子组态, 可能具有γ≈－120°的长椭形状, 在其以上的能级表现出很强的单粒子性，具有复杂的结构. 基带中观测到明显的集体回弯现象, 推转壳模型的计算表明, 此集体回弯是由一对中子的顺排所致, TRS计算表明, 随着转动频率的增加, 核的形状发生明显的变化, 基带中在中子顺排后核具有γ≈－60°的扁椭形状.     

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.