2006年 第23卷 第4期
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 superheavy 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.
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 densitydependent cluster model (DDCM) by including nuclear deformation of the daughter nucleus. A systematic calculation of αdecay halflives 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.
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.
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.
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 beingbuilt superheavy 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.
In the dinuclear system conception, the master equation is solved numerically to calculate the fusion probabilities of superheavy 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 timedependent. The formation cross sections of the superheavy nuclei from Pbbased cold fusion and excitation functions from 48Ca induced hot fusion are reasonably consistent with known experimental data.
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 αparticle 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 halflife 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 “QαN systematics” for the isotopes with Z = 107.
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 multidimensional 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.
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 subbarrier 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.
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 multistep 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.
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 twoparameter Smoluchowski equation. Our results clearly show the isotope dependence of superheavy nucleus production. The formation cross sections of the neutronrich isotope are， generally speaking， obviously enhanced due to the lower Coloumb barrier ， lower height of the conditional saddlepoint， and smaller neutron separation energy.
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 setup 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.
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 halflives of both spherical and deformed nuclei are carried out. A new formula with only four parameters is proposed for proton radioactivity halflives. The halflives 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.
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 manybody 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 lowlying states，under random interactions.