A=130区缺中子核122Cs与134Ce高自旋态研究

通过重离子核反应与在束γ谱的实验技术,对A=130缺中子核区122Cs与134Ce核的高自旋态进行了研究,所用核反应分别为107Ag(19F,1p3n)与122Sn(16O,4n).实验结果扩展了122Cs与134Ce的能级纲图.在122Cs中发现可能是属于手征二重带的结构,而在134Ce核的高自旋态结构中呈现出重要的具有不同γ形变的形状共存特性.Through heavy ion nuclear reaction and in-beam γ-ray spectroscopy technique, the high spin states of neutron-deficient~(122)Cs and~(134)Ce nuclei in A=130 region have been studied. The~(107)Ag(~(19)F, 1p3n) and~(122)Sn(~(16)O, 4n) reactions were used. The previous level schemes of~(122)Cs and~(134)Ce have been extended. Possible chiral doublet bands in~(122)Cs have been observed and a shape coexistence with different γ values in~(134)Ce are suggested.     

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.     

143 Pm高自旋态研究

通过熔合蒸发反应128Te(19F,4nγ)布居了143Pm的高自旋态,利用在束γ谱学方法,对143Pm的高自旋态核结构进行了研究.测量了γ射线单谱和γ-γ符合谱,并进行了γ射线各向异性以及DCO比率分析,建立了激发能高达10535.4keV的能级纲图,其中包括新发现的32条γ射线和17个新能级.用弱耦合模型对143Pm的晕态能级结构进行了解释.     

桨-舵间距和雷诺数对潜艇尾部伴流场均匀性的影响研究

采用Realized k-ε湍流模型求解Reynolds平均Navier-Stokes方程,对SUBOFF全附体模型在低雷诺数和高雷诺数条件下的三维粘性流场分别进行了数值模拟,研究了桨-舵间距以及雷诺数对螺旋桨盘面伴流场的影响.计算结果表明:适当的加大桨-舵间距对提高潜艇尾流场的均匀性有显著的效果;桨-舵间距对潜艇桨盘面伴流场均匀性的影响在潜艇的低雷诺数状态和高雷诺数状态具有同样的规律.     

过渡区核87Zr的高自旋态研究

通过束流能量为118MeV的⁵⁹Co(³²S,3pn)⁸⁷Zr熔合蒸发反应,用在束r谱学方法研究了⁸⁷Zr的高自旋态.利用7台反康普顿谱仪组成的探测阵列进行r–r符合测量,并确定部分r射线的DCO值,在此基础上建立了自旋直到(37/2⁺)和(43/2^－)的能级纲图.观测到了多条新的能级.与相邻的同中子异荷素的比较表明,中子对核结构性质的影响远大于质子的贡献.随着质子数的增加,第一交叉频率呈减小的趋势.     

Efficiency of electrical manipulation in two-dimensional topological insulators

We investigate the efficiency of electrical manipulation in a two-dimensional topological insulator by inspecting the electronic states of a lateral electrical potential superlattice in the system. The spatial distribution of the electron density in the system can be tuned by changing the strength of the externally applied lateral electrical superlattice potential. This provides us the information about how efficiently one can manipulate the electron motion inside a two-dimensional topo- logical insulator. Such information is important in designing electronic devices, e.g., an electric field effect transistor made of the topological insulator. The electronic states under various conditions are examined carefully. It is found that the dispersion of the mini-band and the electron distribution in the potential well region both display an oscillatory behavior as the potential strength of the lateral superlattice increases. The probability of finding an electron in the potential well region can be larger or smaller than the average as the potential strength varies. These features can be attributed to the coupled multiple-band nature of the topological insulator. In addition, it is also found that these behaviors are not sensitive to the gap parameter of the two-dimensional topological insulator model. Our study suggests that the electron density manipulation via electrical gating in a two-dimensional topological insulator is less effective and more delicate than that in a traditional single-band semiconductor.     

Description of the shape evolution in the yrast states of ~（186）Pt

^186Pt was tested in the framework of IBM-1 and the X（3） model. The results show that ^186Pt is located close to the shape phase transition point, but the B（E2） values little agree with the X（3） model. The shape evolution in the yrast states of186Pt is also discussed in detail. TRS calculation exhibits a flat bottomed potential at low spin states, but a relatively deep minimum at high spin states. It suggests that a shape evolution from vibrational mode to rotational mode happens in ^186Pt. The result is in agreement with the E-GOS calculation.     

New band structures in ~（107）Ag

High spin states in ¹⁰⁷Ag are studied via the ¹⁰⁰Mo(¹¹B, 4n)¹⁰⁷Ag reaction at an incident beam energy of 60 MeV. Prompt γ-γ coincidence and DCO ratios are measured by the detector arrays in CIAE. The level scheme has been updated and a new negative band belonging to ¹⁰⁷Ag is identified. The new negative side band has been constructed and its configuration is tentatively assigned to πg_9/2 νh_11/2(g_7/2/d_5/2).     

High-Spin States in Odd-Odd ^140Pr Nucleus

High-spin level structure of doubly odd nucleus ^140Pr has been investigated via the ^130Te(^14N,4n)^140Pr reaction at beam energies from 55 to 65 MeV. Measurements of γ-ray excitation functions, γ-ray singles and γ-γ-t coincidences were performed with twelve BGO(AC)HPGe detectors. The level scheme of ^140Pr, including 27 new levels and 42 new γ rays, has been established for the first time. The level structure is compared with those in the neighbouring odd-odd nuclei, and interpreted qualitatively.     

134Ce核的高自旋态与形状共存

在中国原子能科学研究院H13串列加速器上,通过重离子核反应¹²²Sn(¹⁶O,4n)对A=130缺中子核区的¹³⁴Ce核的高自旋态进行了研究,建立了¹³⁴Ce的新的能级纲图,最高自旋态扩展到22.然而实验结果与近期发表的134Ce核的高自旋态结果不同,所谓在¹³⁴Ce核中存在的磁转动带结构不能被实验证实.对实验结果的分析表明,¹³⁴Ce核的高自旋态结构呈现出重要的形状共存特性在基带以上的回弯处的10+态起源于两个中子组态,基于此10+态的转动带具有γ≈–60°的扁椭形变;另一个10+同质异能态为yrast陷阱,也起源于两中子组态,为具有γ≈–120°的长椭形状;而由两个signature伙伴带组成的强耦合带,则起源于h_11/2与g_7/2质子组态,为具有γ≈0°的长椭形变带.