16O+152Sm、184W准弹和弹性散射的位垒分布

利用¹⁶O束流轰击稳定形变靶¹⁵²Sm和¹⁸⁴W,在背角测量准弹散射和弹性散射激发函数,分别定出准弹和弹性位垒分布D^qel(E)和D^el(E).将结果与从已有的熔合激发函数、自旋分布及其相邻同位素¹⁵⁴Sm和¹⁸⁴W实验得出的位垒分布进行比较,得到相互自洽的结果,同时也用ECIS79程序作了耦合道理论计算.实验表明,靶的变形效应导致位垒分布是非对称的.     

Deformed Potential Energy of ^263Db in a Generalized Liquid Drop Model

The macroscopic deformed potential energy for super-heavy nuclei ^263 Db, which governs the entrance and alphadecay channels, is determined within a generalized liquid drop model (GLDM). A quasi-molecular shape is as-sumed in the GLDM, which includes volume-, surface-, and Coulomb-energies, proximity effects, mass asymmetry,and an accurate nuclear radius. The microscopic single particle energies are derived from a shell model in anaxially deformed Woods-Saxon potential with a quasi-molecular shape. The shell correction is calculated by theStrutinsky method. The total deformed potential energy of a nucleus can be calculated by the macro-microscopicmethod as the summation of the liquid-drop energy and the Strutinsky shell correction. The theory is appliedto predict the deformed potential energy of the experiment ^22Ne ^241Am→^263Db^*→^259Db 4n, which wasperformed on the Heavy Ion Accelerator in Lanzhou. It is found that the neck in the quasi-molecular shape isresponsible for the deep valley of the fusion barrier due to the shell corrections. In the cold fusion path, thedouble-hump fusion barrier is predicted by the shell correction and complete fusion events may occur.     

核ANC的激发态中子晕

利用转移反应^11B(d,p)^12 B和^12C(d,p)^13C 抽取^12B→^11B n和^13C←^12C n重叠函数的核渐归一化常数，计算了^12Ｂ和^13C核中子密度分布的均方根半径及其在核外的几率。实验结果表明，^12B的第二（J^π=2^-），第三（J^π=1^-）激发态和^13C的第一（J^π=1/2^ ）激发态为中子晕态，而^13C的第三（J^ π=5/2^ )激发态是中子皮态。考察了库仑势和角动量对晕形成的阻碍效应.提出了均方根半径对于有效核子分离的统一的标度定律。     

亲和力对熔合反应位垒的影响

熔合反应的宏观形变位能由推广的液滴模型来确定,它包括体积能、表面能、库容能、亲和力效应、质量的不对称性和精确的核半径.在过去裂变研究中,人们假定表面能和库仑能控制着位垒的高度和宽度.表面能也只考虑表面张量力效应,并不包括颈部或刚形成的碎片的表面之间吸引核力的贡献.在推广的液滴模型中,亲和力考虑了这些附加的表面效应.在两个核的接触点,亲和能达到最大值,它的两边逐渐减少直到零.亲和能减少位垒的高度并移动位垒峰的位置,它对应于吸引的亲和力和排斥的库仑力之间平衡的两个分开碎片的位置.研究表明:对于超重核熔合过程,亲和能使得宏观形变位能有一个宽的坑(pocket),它对应于核的大形变.对于轻的核–核系统,这种现象不出现.     

Alpha Decay Half-Lives of New Superheavy Elements through Quasimolecular Shapes

The lifetimes of a decays of the recently produced isotopes of the elements 112, 114, 116 and the element ^294118 and of some decay products have been calculated theoretically within the Wentzel-Kramers-Brillouin approximation. The a decay barriers have been determined in the quasimolecular shape path within a generalized liquid drop model including the proximity effects between nuclei in a neck, the mass and charge asymmetry and the precise nuclear radius. These calculations provide reasonable estimates for the observed a decay lifetimes. The calculated results have been compared with the results of the density-dependent M3Y effective interaction and the experimental data. It is indicated that the theoretical foundation of the generalized liquid drop model is as good as that of the microscopic DDM3Y model, at least in the sense of predicting the T1/2 values as long as one uses a correct a decay energy. The half lives of these new nuclei are well tested from the consistence of the macroscopic, the microscopic and the experimental data.     

垒下熔合裂变中观察到的异常

测量了¹⁶O+²³²Th、²³⁸U和¹⁹F+²³²Th近垒和垒下熔合裂变截面以及碎片角分布.包含靶核静态形变的耦合道理论解释了垒下熔合截面增强,预言了复合核系统自旋分布展宽.而实验上观察到的碎片角分布各向异性明显与裂变统计理论的预言不一致.     

程函波函数对准自由散射6Li（p,pd）α的应用

近似地用程函波函数作为粒子在原子核作用下的扭曲波函数,分析了入射能量为156MeV、590MeV与670MeV的质子对原子核⁶Li引起的准自由散射⁶Li（p,pd）α。从156MeV的情况可看到,用程函波函数来研究准自由散射所得的结果和用分波法得到的结果同样使人满意。对590MeV与670MeV的情况,所得结果与平面波冲量近似相比有所改进。     

Development of large-area quadrant silicon detector for charged particles

The quadrant silicon detector, a kind of passivated implanted planar silicon detector with quadrant structure on the junction side, gained its wide application in charged particle detection. In this paper, the manufacturing procedure, performance test and results of the quadrant silicon detector developed recently at the China Institute of Atomic Energy are presented. The detector is about 300 μm thick with a 48 mm×48 mm active area. The leakage current under the full depletion bias voltage of -16 V is about 2.5 nA, and the rise time is better than 160 ns. The energy resolution for a 5.157 MeV α-particle is around the level of 1%. Charge sharing effects between the neighboring quads, leading to complicated correlations between two quads, were observed when α particles illuminated on the junction side. It is explained as a result of distortion of the electric field of the inter-quad region. Such an event is only about 0.6% of all events and can be neglected in an actual application.     

双折叠模型对相互作用势实部的计算

用双折叠模型计算了核核碰撞的相互作用势, 其中核子-核子相互作用势采用M3Y-Reid和M3Y-Paris形式, 交换部分考虑了有限力程的密度依赖的核子-核子相互作用, 程序用于重离子散射光学势实部的计算. 回顾了折叠模型的普遍特征和讨论了理论计算过程, 对各种类型的核子-核子相互作用下计算的相互作用势进行比较, 发现双折叠模型对大部分系统相互作用势的实部取得了满意的结果. 因此这个工作为重离子相互作用势的折叠计算提供了很好的方法.     

近垒重离子熔合反应中的中子转移效应(英文)

近势垒及其以下能区重离子熔合反应中的中子转移耦合道效应是一个复杂且有争议的问题。简要介绍了近年来在中国原子能科学研究院的HI-13串列加速器上,基于静电偏转板装置完成的32S+90,94,96Zr,18O+74Ge和18O+58Ni等几个典型体系的熔合反应研究情况,并结合耦合道理论对实验数据进行了分析。选取反应体系时同时关注了正Q值的中子拾取和削裂道。另外,基于完全耦合道理论计算,提出了一种能够定量提取熔合反应中中子转移效应的自洽方法。这些研究进一步证实了垒下重离子熔合反应中的中子转移效应,同时指出了其复杂性。需要进一步的实验和理论研究来澄清相关核反应机制。The effect of neutron transfers on near-and sub-Coulomb-barrier fusion of heavy-ions is still a complicated and controversial problem. This paper reviews the recent experimental results of the fusion excitation functions of several typical systems, which have been measured by using an electrostatic deflector setup at the HI-13 tandem accelerator of CIAE. Both the neutron pickup and stripping effects were studied. Moreover, a self-consistent method to reliably isolate the transfer effect quantitatively based on the coupledchannels calculation is proposed. These studies give a further support for the neutron transfer effect on sub-barrier fusion of heavy-ions and its complexity. Further experimental and theoretical studies are needed for clarifying the relevant reaction mechanisms.