QMD模型的改进及其在低能重离子反应中的应用

丰中子核以及重核熔合机制的研究以及中能重离子碰撞中多重碎裂的研究都迫切需要一个统一的、自洽的微观动力学模型.经过对量子分子动力学模型进行根本的改进,发展了一个新的、适用于低能以及中能重离子反应的统一描述的微观动力学模型.改进的量子分子动力学(ImQMD)模型能够将整个熔合反应过程中的动力学效应、同位旋效应以及弹靶质量不对称效应等比较全面地、自洽地考虑进来,从而给熔合反应的研究提供了一个新的途径.ImQMD模型能够很好地再现一系列核的基态性质以及10多个熔合反应的激发函数(包括丰中子核熔合体系以及实验最新测量的132Sn+64Ni熔合体系).此外还运用该模型初步探索了重核熔合过程中复合体系的寿命与体系的入射能量、体系大小以及体系的中子质子比的依赖关系. We have developed a new microscopic dynamical model called improved quantum molecular dynamical model (ImQMD). This model can describe the fusion process at energies near the Coulomb barrier as well as the multifragmentation process at intermediate energies in heavy-ion collision (HIC) uniformly. By using this model, fusion cross sections (including some of neutron-rich nuclei reactions and that of newly measured~(132)Sn+~(64)Ni fusion reaction) of tens reactions can be reproduced remarkably well. In fusi...     

相对论重离子反应的热化过程

本文从相对论BUU理论出发研究了1GeV/n能区重离子反应全局(global)和局域(local)平衡性质,计算表明在该能区平均场对反应动力学过程仍有相当的作用;对有限核系统的反应动力学过程的时间演化的研究表明,有限核系统无论全局的还是局域的平衡均未能达到完全平衡,因而对有限核系统重离子反应基于完全热平衡概念的适用性值得怀疑.     

40Ca±1核的l-禁戒M1跃迁和有效g因子

用⁴⁰Ca区域的有效g因子计算了⁴⁰Ca±1核的l-禁戒M1跃迁强度。结果解释了³⁹K,⁴¹K的异常大的l-禁戒M1跃迁强度。对³⁹K,⁴¹K和³⁹Ca,⁴¹Ca的跃迁强度的差别作了定性的解释。     

核场论中声子重整化的初步研究

本文在声子固有自能子图取为图1(1)的情况下,写出了重整化声子的戴逊方程,得到了重整化声子的本征方程,以及声子和规则与声子权重能量和规则。     

Modified Woods-Saxon Potential for Heavy-Ion Fusion Reaction

A modified Woods-Saxon （MWS） potential is proposed for describing nucleus-nucleus interaction based on the Skyrme energy-density functional approach. Fusion barriers for a large number of fusion reactions from light to heavy systems can be described well with this potential. The suitable incident energies for fusion reactions leading to superheavy nuclei are also explored. It seems to us that the MWS potential is useful for selecting the suitable incident energies for fusion reactions for producing super-heavy nuclei.     

Disentangling the Effects of Thickness of the Neutron Skin and Symmetry Potential in Nucleon Induced Reactions on Sn Isotopes

The effects of density dependence of symmetry energy and the thickness of the neutron skin in proton （neutron） induced reactions on Sn isotopes are investigated by means of the improved molecular dynamics model. The investigation shows that the target size dependence of the reaction cross sections for proton induced reactions on Sn isotopes is sensitive to the density dependence of the symmetry energy and less sensitive to the thickness of the neutron skin of the target nuclei, but that, for neutron induced reactions on Sn isotopes, it is less sensitive to the density dependence of the symmetry energy and sensitive to the thickness of the neutron skin of the target nucleus.     

Probing the Dissipation Mechanism in Ternary Reactions of ^197Au＋^197Au by Mean Free Path of Nucleons

the collision of very heavy nuclei ^197Au＋^197Au at 15AMeV has been studied within the improved quantum molecular dynamics model. A class of ternary events satisfying nearly complete balance of mass numbers is selected. The experimental mass distributions for the system ^197Au＋^197Au ternary fission fragments, the heaviest（A1）, the intermediate （A2） and the lightest （A3）, are reproduced well. The mean free path of nucleons in the reaction system is studied and the shorter mean free path is responsible for the ternary fission with three mass comparable fragments, in which the two-body dissipation mechanism plays a dominant role.     

重离子熔合势垒的动力学模型研究

在改进的量子分子动力学模型基础上系统地研究了超重核合成中的入射道静态势和动力学势.从入射道静态势给出了质量不对称度与静态势垒高度以及质量不对称度与接触点驱动势的关系.动力学势垒高度是能量依赖的,随着入射能量的增加而增加,最终趋近于密度冻结势垒高度;动力学势垒高度随着入射能量的降低而降低,它的最低值接近于绝热势垒高度.在冷熔合反应中,动力学势垒的最低值所对应的入射能量可能是合成超重元素最佳入射能的选择     

相对论重离子碰撞中的K+产生及集体流

用自洽的相对论BUU模型研究了相对论重离子碰撞的K⁺产生及流,研究结果表明K⁺集体流在相对论重离子碰撞中对核态方程(EOS)和K–N标量吸引项(∑_KN)是敏感的,在对K⁺流中心度依赖的研究中发现在大碰撞参数时有反向流出现,可为确定∑_KN值提供更为有效的信息.对K⁺产生的总产额及各个不同道的贡献与EOS和∑_KN关系进行了细致分析,表明N△道对K⁺产生的贡献和影响都是最显著的; 不同道的贡献对∑_KN的灵敏程度不同,其中∑_KN对N△道的影响要比对πB道的大.