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2006年  第23卷  第4期

第五届“超重核研究”研讨会论文集
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第五届“超重核研究”研讨会论文集
近代物理研究所超重核研究现状及计划
徐瑚珊, 黄天衡, 孙志宇, 胡正国, 詹文龙, 周小红, 黄文学, 张宏斌, 章学恒, 甘再国, 郑川, 李君清, 马新文, 秦芝, 肖国青, 郭忠言, 李智慧, 张玉虎, 靳根明
2006, 23(4): 359-368. doi: 10.11804/NuclPhysRev.23.04.359
摘要:
简单描述了超重核合成的历史与国际现状, 详细地介绍了近代物理研究所已经开展的研究工作及取得的成果, 并对近代物理研究所未来在超重核研究方面的研究计划进行了介绍。 The history and the international status of the superheavy nuclei synthesis are briefly described. The related research work carried out at the Institute of Modern Physics (IMP) has been reviewed. The prospect of the super heavy nuclei research at IMP has been introduced.
超重核α衰变寿命的理论研究
任中洲, 许昌
2006, 23(4): 369-373. doi: 10.11804/NuclPhysRev.23.04.369
摘要:
建立了计算球形核α衰变寿命的新模型——密度依赖的结团模型(DDCM)。在此基础上,通过引入子核的形变自由度,发展了形变的密度依赖的结团模型, 编写了形变的DDCM程序。并系统计算了Z=106—110的超重核α衰变寿命。通过与已有的实验数据的对比分析, 发现理论结果和实验数据符合得很好,验证了DDCM在超重核区域的适用性。
We proposed a deformed version of densitydependent cluster model (DDCM) by including nuclear deformation of the daughter nucleus. A systematic calculation of αdecay halflives of superheavy nuclei (Z=106—110) is carried out by the deformed DDCM. The good agreement between theory and data is obtained. It is shown that the deformed DDCM works well in the superheavy mass region.
研究重元素原子谱学性质的可能性
靳根明, 冯兆庆, 付芬, 赵旭林
2006, 23(4): 374-381. doi: 10.11804/NuclPhysRev.23.04.374
摘要:
论述了重元素,特别是超重元素原子谱学的重要意义。指出了对这些元素原子谱学进行研究的必要性。探讨了通过核反应产生重元素的几率和产额, 以及可能的收集方法,表明了这可为重元素原子谱学研究提供必要的条件。 同时也简单描述了研究重原子谱学的方法——激光共振电离法。
The importance of the atomic spectroscopy of heavy elements,especially the superheavy elements has been briefly reviewed. It is pointed that studies of the atomic spectroscopy of very heavy elements is necessary from the atomic physics and the identification of new superheavy elements. The production probability and yields of heavy elements in the heavy ion induced reactions were discussed. And the possible collection methods for heavy residue of reactions were also retrospected. Those techniques which have been used in the heavy ion reactions and superheavy element identifications will provide some possible support to the studies of heavy element spectroscopy.
超重核合成理论模型简介
左维, 李君清, 赵恩广
2006, 23(4): 382-385. doi: 10.11804/NuclPhysRev.23.04.382
摘要:
介绍并讨论了研究超重核合成的主要理论模型以及近年来在研究重核熔合机制和超重核合成理论模型方面的进展。 The theoretical models for investigating the fusion mechanism of heavy nucleus collisions and calculating the formation cross sections of superheavy nuclei have been introduced. The recent development and the present status for understanding the fusion mechanism of heavy nucleus collisions have been discussed.
超重核研究谱仪的RFQ冷却聚束器RFQ1L
黄文学, 王玥, 朱志超, 田玉林, 徐瑚珊, 孙志宇, 肖国青, 詹文龙
2006, 23(4): 386-395. doi: 10.11804/NuclPhysRev.23.04.386
摘要:
介绍了超重核研究谱仪中RFQ冷却聚束器RFQ1L的结构和运用SIMION程序对离子的冷却、聚束、引出和撇气过程的模拟情况。 模拟显示: 通过仔细选择工作点就完全可以把经过充气反冲质量分离器分离后的低品质束流转化为斑点小、发射度小和能量单一的高品质束流, 为紧接其后的磁铁和激光高效率分析提供条件。The structure and the simulation results about the cooling,bunching,extraction and skimming of the RFQ cooler and buncher RFQ1L, which is an important part of the beingbuilt superheavy nuclide research spectrometer, have been introduced. It shows that, by careful choice of its working point, we can obtain an ion beam with small beam spot, small emittance and mono energy, which can satisfy the requirements of the successive analyses by dipole and laser with high efficiencies.
重离子碰撞中超重核的形成机制(英文)
李君清, 左维, 冯兆庆, 靳根明, 赵恩广
2006, 23(4): 396-398. doi: 10.11804/NuclPhysRev.23.04.396
摘要:
在双核模型框架下,用数值解主方程方法计算了超重核的熔合几率。 明确描述了包含能量、角动量和碎片形变弛豫的相对运动,并与核子扩散过程相耦合。因此,用微观方法推导出的核子跃迁几率是与时间相关的。所计算的以Pb为靶的冷熔合超重核形成截面和以48Ca为弹核的热熔合超重核形成激发函数与已知的实验值在合理的范围内符合。
In the dinuclear system conception, the master equation is solved numerically to calculate the fusion probabilities of superheavy nuclei. The relative motion concerning the energy, the angular momentum and the fragment deformation relaxations is explicitly treated to couple with the diffusion process. The nucleon transition probabilities, which are derived microscopically, are related with the energy dissipation of the relative motion, thus they are timedependent. The formation cross sections of the superheavy nuclei from Pbbased cold fusion and excitation functions from 48Ca induced hot fusion are reasonably consistent with known experimental data.
超重核密度的计算
裴俊琛, 许甫荣#
2006, 23(4): 399-403. doi: 10.11804/NuclPhysRev.23.04.399
摘要:
用SkyrmeHartreeFock模型计算了超重核的密度分布,并讨论了其形状和同位旋相关性。 以292120核为例,计算表明形变对密度分布有相当大的影响。
266Bh的α衰变性质研究(英文)
秦芝, 吴晓蕾, 丁华杰, 吴王锁, 黄文学, 雷祥国, 徐岩冰, 袁晓华, 郭斌, 杨维凡, 甘再国, 范红梅, 郭俊盛, 徐瑚珊, 肖国青
2006, 23(4): 404-407. doi: 10.11804/NuclPhysRev.23.04.404
摘要:
报道了利用兰州重离子研究装置提供的26Mg重离子束流轰击243Am靶产生和鉴别已知超重核素266Bh的实验结果。利用转轮收集探测装置依靠母子核遗传关系通过观测Bh同位素与其子核Db和Lr之间的α-α关联事件来鉴别266Bh。实验中观测到266Bh的α能量为(9.03 ± 0.08)MeV, 与日本理化学研究所在合成113号元素中第一个衰变链中观测到266Bh的α能量为9.07 MeV相近。 266Bh的半衰期为0.66+0.59-0.26 s, 从实验得到的Qα也符合Z=107的Qα随中子数变化的系统性The isotope of 266Bh was produced and identified definitely in bombardments of 243Am target with 162 MeV 26Mg ions at HIRFL. Identification was made by observation of correlated αparticle decays between the Bh isotopes and their Db and Lr daughters using a rotating wheel system. The measured α energy for 266Bh is (9.03±0.08) MeV, and this value close to the 9.07 MeV for 266Bh observed in the first chain of element 113 at RIKEN. The halflife of 266Bh is 0.66+0.59 -0.26 s. The Qα value derived from this experiment fits well into the general trend in a “QαN systematics” for the isotopes with Z = 107.
关于重核强阻尼反应的研究
吴锡真, 田俊龙, 李祝霞, 王宁, 赵凯, 张英逊, 欧立
2006, 23(4): 408-412. doi: 10.11804/NuclPhysRev.23.04.408
摘要:
讨论了重核碰撞形成巨复合体系破裂的强阻尼反应产生超重核的问题。 评述了两种主要的理论模型: 唯象的多维朗之万模型和本课题组发展的微观输运理论模型。 概括阐述了微观输运理论研究反应 197Au+197Au , 238U+238U和244Pu+244Pu等的主要结果。 给出了反应中产生的超重碎块的几率与入射能的关系, 复合体系和超重碎块的衰变机制以及所形成的超重碎块的结合能和形状的分布。 In this paper, the possibility of producing superheavy fragments through strongly damped reactions in very massive nuclear collisions is investigated. Two theoretical models, which are the phenomenologically multidimensional Langevin equation model and improved quantum molecular dynamics model developed recently by our group, are briefly reviewed. The dependence of the production probability of superheavy fragments on the incident energy, the decay mechanism of the composite systems and superheavy fragments, and the distributions of the binding energy and shapes of superheavy fragments are iscussed for reactions of 244Pu+244Pu, 238U+238U, 197Au+197Au based on the improved quantum molecular dynamics model.
近垒能量下重核熔合几率的量子路径积分计算
包景东
2006, 23(4): 413-417. doi: 10.11804/NuclPhysRev.23.04.413
摘要:
针对近垒能量下经典涨落耗散模型预期的重核熔合几率比实验结果偏小的问题, 发展了一种实时间路径积分方法并用于研究重核熔合激发函数, 给出了包含量子涨落效应的解析表达式。 计算了几个对称和近似对称反应系统的熔合几率, 结果表明理论结果与实验值符合较好。 还讨论了颈部增长对熔合障碍的影响。 A real time path integral approach is developed in order to work out a correct solution to a problem for the smaller result of the fusion probability of heavy nuclei based on the classical diffusion model at subbarrier energies. An analytical expression for the quantum fusion probability is proposed,which contains the quantum fluctuation effect. The fusion probabilities of several symmetrical and approximate symmetrical systems are calculated, the heoretical results are in agreement with the experimental data. The influence of the neck length and its fluctuation upon the fusion hindrance is discussed.
直接鉴别超重元素Z和A的一种新的可能方法
马新文, 詹文龙, 张大成
2006, 23(4): 418-422. doi: 10.11804/NuclPhysRev.23.04.418
摘要:
随着合成的超重元素向超重岛逼近,合成截面越来越小,同时,合成的超重元素的寿命可能相对增长, 这对利用α衰变链的传统方法鉴别超重元素是非常不利的。 讨论了可能突破这个瓶颈的一种可以直接鉴别超重元素原子序数Z和质量A的新方法, 即与RFQ离子阱技术相结合的激光多步共振电离方法, 对实现这种方法的途径、 该方法所面临的困难和挑战、需要进行的前期研究工作以及该方法的可能性和可行性进行了较详细的讨论。
With the synthesis of heavy elements approaching the super heavy island, the production cross section becomes smaller and the lifetime of the super heavy element becomes longer, which results in the difficulties for identification of theelements by using conventional alpha decay chain technique. In order to overcome the difficulties, a novel approach to direct identification of atomic number Z and nuclear mass A for super heavy elements is proposed, namely, the multistep resonant laser ionization of singly charged ions in combination with RFQ trap. The routine for the experiment is presented, and the possibilities, feasibilities, as well as the problems to be faced, are discussed in detail.
超重核合成的同位素依赖探讨
刘祖华, 包景东
2006, 23(4): 423-425. doi: 10.11804/NuclPhysRev.23.04.423
摘要:
利用二参量Smoluchowski方程计算了54Fe+204Pb,56Fe+206Pb,58Fe+208Pb冷熔合和32,34,36S+238U热熔合的复合核形成截面和蒸发残余截面, 结果清楚地显示出超重核合成截面随同位素的变化。 由于较低的入射道库仑位垒、 较低的不对称裂变谷中的条件鞍点和较小的中子分离能, 一般地说, 丰中子同位素的超重核形成截面明显增强。
The cross sections of the compound nucleus formation and e vaporation residue for the 54Fe+204Pb, 56Fe+206Pb, 58Fe+208Pb cold fusion and 32,34, 36S+238U hot fusion have been calculated by using a twoparameter Smoluchowski equation. Our results clearly show the isotope dependence of superheavy nucleus production. The formation cross sections of the neutronrich isotope are, generally speaking, obviously enhanced due to the lower Coloumb barrier , lower height of the conditional saddlepoint, and smaller neutron separation energy.
40Ar+238U 实验介绍
范红梅, 黄明辉, 甘再国, 郭俊盛, 吴晓蕾, 郭斌, 秦芝, 邬智君, 黄天衡, 谢成营, 王华磊, 宋立涛
2006, 23(4): 426-429. doi: 10.11804/NuclPhysRev.23.04.426
摘要:
主要介绍了利用兰州重离子加速器提供的270 MeV的40Ar离子束轰击238U靶,通过熔合蒸发反应进行试合成Z=110附近的新同位素的实验情况。分析了目前关于超重核研究的现状并描述了这次实验的目的、 可行性分析、 实验装置以及实验过程等。本次实验仍然用氦喷嘴技术对产物进行传输, 并用一套具有数对探测器组的转轮收集探测系统对产物进行收集和测量。
The state of the experiment to produce the new isotopes around Z=110 are presented in this paper. The emphasis is laid upon introducing the experiment purpose, the setup and the feasibility for producing this objective nuclide. In the experiment the new isotopes were produced by the complete fusion evaporation reaction of 238U with 270 MeV 40Ar at the Sector Focus Cyclotron (SFC) of Heavy Ion Research Facility in Lanzhou(HIRFL). The reaction products were also transported and collected by using the helium jet technique and rotating wheel apparatus.
关于极端原子核的相对论自洽角动量投影壳模型计算(英文)
李岩松, F. H. AL-Khudair
2006, 23(4): 430-432. doi: 10.11804/NuclPhysRev.23.04.430
摘要:
相对论自洽角动量投影壳模型是最近发展出来的一个自洽模型, 它对于不同核区具有稳定的参数, 能够很好地描述已知和未知具有稳定形变的各种原子核的性质。 计算了若干包括稳定核素、 极端核素和超重核素, 并把计算结果与现有的实验数据进行了比较。
质子放射性寿命的新规律
许昌, 任中洲
2006, 23(4): 433-435. doi: 10.11804/NuclPhysRev.23.04.433
摘要:
对球形核和变形核质子放射性的半衰期进行了系统的分析和研究,提出了新的计算质子放射性寿命的解析公式。 通过对公式计算寿命和实验测量值的系统比较,发现两者之间符合得非常好,说明新公式十分准确并具有良好的预言能力。 Systematic calculations on proton radioactivity halflives of both spherical and deformed nuclei are carried out. A new formula with only four parameters is proposed for proton radioactivity halflives. The halflives calculated by using the new formula are in good agreement with the experimental ones. The new formula is simple but accurate, which is very useful for further experiments.
随机相互作用的原子核等多体系统的性质
赵玉民
2006, 23(4): 436-439. doi: 10.11804/NuclPhysRev.23.04.436
摘要:
讨论了随机相互作用下原子核等多体系统的基态和低激发态性质研究方面的进展情况。 In this paper it is discussed the regularities of manybody systems such as nuclei in the presence of random interaction. In particular,it concentrates on the present status towards understanding of spin zero ground state dominance,energy centroids of certain quantum number(s) such as spin, behavior of lowlying states,under random interactions.