2003年 第20卷 第2期
2003, 20(2): 71-75.
doi: 10.11804/NuclPhysRev.20.02.071
摘要:
回顾了超重元素研究的现状和超重元素合成反应机制研究的发展,指出目前超重元素合成研究中存在的困难和对超重余核鉴别的一些设想.对近对称反应系统的熔合反应机制进行了较深入的讨论,建议对这类反应生成复合核的截面进行理论和实验上的研究.The status and development of the studies on reaction mechanism for synthesis of superheavy elements has been reviewed. In this paper it is pointed out the difficulties existing in the studies and synthesis of superheavy elements and some conceives for measurement and identification of very heavy residues. The fusion of nearsymmetric reaction systems is discussed and proposed to do more investigations on the fusion cross sections of these reactions on both theory and experiment.
回顾了超重元素研究的现状和超重元素合成反应机制研究的发展,指出目前超重元素合成研究中存在的困难和对超重余核鉴别的一些设想.对近对称反应系统的熔合反应机制进行了较深入的讨论,建议对这类反应生成复合核的截面进行理论和实验上的研究.The status and development of the studies on reaction mechanism for synthesis of superheavy elements has been reviewed. In this paper it is pointed out the difficulties existing in the studies and synthesis of superheavy elements and some conceives for measurement and identification of very heavy residues. The fusion of nearsymmetric reaction systems is discussed and proposed to do more investigations on the fusion cross sections of these reactions on both theory and experiment.
2003, 20(2): 76-90.
doi: 10.11804/NuclPhysRev.20.02.076
摘要:
简单介绍了超重核合成的历史,详细讨论了目前超重核合成最成功的技术路线,包括产生方法、分离手段以及探测技术,并就各种技术的优缺点进行了比较.探讨了目前超重核研究所面临的困难以及介绍了国际上几个主要相关实验室的研究动态,并对超重核研究的发展趋势做了简单展望. The history of the synthesis of the transuranium nuclei is briefly introduced. The most successful techniques currently used for synthesizing superheavy nuclei are surveyed and discussed in detail. The drawbacks and the problems for reaching the stability island of superheavy nuclei with the techniques currently used are discussed. The present status and perspectives of the super heavy nuclei research at different laboratories are also introduced. Finally, a brief prospect on the trends...
简单介绍了超重核合成的历史,详细讨论了目前超重核合成最成功的技术路线,包括产生方法、分离手段以及探测技术,并就各种技术的优缺点进行了比较.探讨了目前超重核研究所面临的困难以及介绍了国际上几个主要相关实验室的研究动态,并对超重核研究的发展趋势做了简单展望. The history of the synthesis of the transuranium nuclei is briefly introduced. The most successful techniques currently used for synthesizing superheavy nuclei are surveyed and discussed in detail. The drawbacks and the problems for reaching the stability island of superheavy nuclei with the techniques currently used are discussed. The present status and perspectives of the super heavy nuclei research at different laboratories are also introduced. Finally, a brief prospect on the trends...
2003, 20(2): 91-95.
doi: 10.11804/NuclPhysRev.20.02.091
摘要:
讨论了超重核形成截面计算中的耦合道效应、壳效应的阻尼效应、能级密度的集体运动增强因子以及蒸发残余核的自旋分布等几个重要问题,并给出相应的实验结果.因这些因素都可能对截面有数量级的影响,正确处理与否直接关系到超重核合成截面理论预言的可靠性. .Several important aspects in the cross section calculations for the synthesis of superheavy nuclei have been inquired. They are the effects of the coupledchannels, the damping of shell correction energy, the collective enhancements in the level density and the spin distributions of evaporation residues. The channel coupling of relative motion with internal degrees of freedom will enhance significantly the capture cross section at subbarrier energies. However, recent measurements of spin distributions for ...
讨论了超重核形成截面计算中的耦合道效应、壳效应的阻尼效应、能级密度的集体运动增强因子以及蒸发残余核的自旋分布等几个重要问题,并给出相应的实验结果.因这些因素都可能对截面有数量级的影响,正确处理与否直接关系到超重核合成截面理论预言的可靠性. .Several important aspects in the cross section calculations for the synthesis of superheavy nuclei have been inquired. They are the effects of the coupledchannels, the damping of shell correction energy, the collective enhancements in the level density and the spin distributions of evaporation residues. The channel coupling of relative motion with internal degrees of freedom will enhance significantly the capture cross section at subbarrier energies. However, recent measurements of spin distributions for ...
2003, 20(2): 96-98.
doi: 10.11804/NuclPhysRev.20.02.096
摘要:
分析了目前关于超重核研究的现状,结合现有的设备及条件,在合成259Db以后,下一次实验的目标核初步确定为107号元素的新同位素265Bh.描述了对MG转轮收集探测系统的实验检验结果.实验中成功地观察和测量了24Mg+232Th的产物252No的母子体的α衰变谱,为下一步合成265Bh完成了部分预实验工作.另外,也给出了下一个目标核的衰变特性的理论预言值,同时也选择了产生该目标核的弹靶组合及反应道,并对生成截面进行了粗略估计,给出了该核的可观测性产额及可行性分析. The present status of investigation on the surperheavy nuclei are analyzed. After 259Db synthesized, the next objective nuclide is determined to be265Bh, a new isotope of Z=107 element, according to our existing available equipment and conditions.The test result of the MG rotating wheel collection and detection system is described. The αdecay spectra of motherdaughter of the product252No from24Mg +232Th reaction are observed and measured successfully in this test experiment. It is regarde...
分析了目前关于超重核研究的现状,结合现有的设备及条件,在合成259Db以后,下一次实验的目标核初步确定为107号元素的新同位素265Bh.描述了对MG转轮收集探测系统的实验检验结果.实验中成功地观察和测量了24Mg+232Th的产物252No的母子体的α衰变谱,为下一步合成265Bh完成了部分预实验工作.另外,也给出了下一个目标核的衰变特性的理论预言值,同时也选择了产生该目标核的弹靶组合及反应道,并对生成截面进行了粗略估计,给出了该核的可观测性产额及可行性分析. The present status of investigation on the surperheavy nuclei are analyzed. After 259Db synthesized, the next objective nuclide is determined to be265Bh, a new isotope of Z=107 element, according to our existing available equipment and conditions.The test result of the MG rotating wheel collection and detection system is described. The αdecay spectra of motherdaughter of the product252No from24Mg +232Th reaction are observed and measured successfully in this test experiment. It is regarde...
2003, 20(2): 99-101.
doi: 10.11804/NuclPhysRev.20.02.099
摘要:
利用SFC提供的束流对新建的转轮系统进行了检验实验,得到了相关的实验结果.实验证明了该装置的可靠性,为进一步开展超重核的研究完成了预实验.A new setup was built in IMP. The reaction 24Mg+232Th was performed as a test experiment for this setup. The decaychains of 252No and 253No have been observecl in this reaction. The results show that this setup is efficient for the rear events and it is possible to use this setup in the future experiment.
利用SFC提供的束流对新建的转轮系统进行了检验实验,得到了相关的实验结果.实验证明了该装置的可靠性,为进一步开展超重核的研究完成了预实验.A new setup was built in IMP. The reaction 24Mg+232Th was performed as a test experiment for this setup. The decaychains of 252No and 253No have been observecl in this reaction. The results show that this setup is efficient for the rear events and it is possible to use this setup in the future experiment.
2003, 20(2): 102-110.
doi: 10.11804/NuclPhysRev.20.02.102
摘要:
简单介绍了近年来在超重核研究方面所取得的成就和理论方面所面临的挑战.着重介绍推广的液滴模型和准分子形状机制,它们的优点是考虑了精确的核半经、质量和电荷的不对称性、形变、亲和力和温度等.推广的液滴模型和准分子形状机制能很好地描述重核和超重核的裂变、衰变及完全熔合反应.The progress and challenge on studies of superheavy elements both experiments and theories has been briefly introduced. It is emphasis to introduce a generalized liquid drop model, including the proximity effects, the asymmetry, an accurate nuclear radius, and quasi molecular shapes. The α decay halflives of 373 nuclei and superheavy elements have been calculated in the generalized liquid drop model and compared with the available experimental data. The deformed energies have also been obtained ...
简单介绍了近年来在超重核研究方面所取得的成就和理论方面所面临的挑战.着重介绍推广的液滴模型和准分子形状机制,它们的优点是考虑了精确的核半经、质量和电荷的不对称性、形变、亲和力和温度等.推广的液滴模型和准分子形状机制能很好地描述重核和超重核的裂变、衰变及完全熔合反应.The progress and challenge on studies of superheavy elements both experiments and theories has been briefly introduced. It is emphasis to introduce a generalized liquid drop model, including the proximity effects, the asymmetry, an accurate nuclear radius, and quasi molecular shapes. The α decay halflives of 373 nuclei and superheavy elements have been calculated in the generalized liquid drop model and compared with the available experimental data. The deformed energies have also been obtained ...
2003, 20(2): 111-115.
doi: 10.11804/NuclPhysRev.20.02.111
摘要:
在双核系统框架下,通过数值法解主方程计算了双核间的核子跃迁全熔合几率.两碰撞核内部激发能由相对运动能损提供,因此能够将核子转移过程与相对运动耦合起来.对一些以Pb为靶的形成超重核的冷熔合反应,计算了最佳激发能、形成双核系统的俘获截面、复合核形成几率及存活几率等,所得到的形成超重核蒸发剩余截面与已知实验值符合较好. In the concept of Dinuclear system (DNS) the complete fusion probability of two touch nuclei via nucleon transfer is described by numerically solving the Master equation. The excitation energy of two colliding nuclei is supplied by the energy dissipation of their relative motion, thus the nucleon transfer process and the relative motion are coupled. For Pb based cold fusion reactions to form super heavy nuclei, the optimal excitation energy, the capture crosssection to form a DNS ...
在双核系统框架下,通过数值法解主方程计算了双核间的核子跃迁全熔合几率.两碰撞核内部激发能由相对运动能损提供,因此能够将核子转移过程与相对运动耦合起来.对一些以Pb为靶的形成超重核的冷熔合反应,计算了最佳激发能、形成双核系统的俘获截面、复合核形成几率及存活几率等,所得到的形成超重核蒸发剩余截面与已知实验值符合较好. In the concept of Dinuclear system (DNS) the complete fusion probability of two touch nuclei via nucleon transfer is described by numerically solving the Master equation. The excitation energy of two colliding nuclei is supplied by the energy dissipation of their relative motion, thus the nucleon transfer process and the relative motion are coupled. For Pb based cold fusion reactions to form super heavy nuclei, the optimal excitation energy, the capture crosssection to form a DNS ...
2003, 20(2): 116-120.
doi: 10.11804/NuclPhysRev.20.02.116
摘要:
用Skyrme Hartree Fock+BCS方法计算了超重核的基态性质,讨论了结合能、α衰变、形变、壳结构和自发裂变等问题.计算得到的结合能较好地反映了实验测量值,α衰变能与实验值符合很好.发现基本上有两种类型的超重核形变:在270108核附近的β2≈0.2的长椭球形变和在298114核附近的近球形形变.单粒子能级分布计算表明:在质子Z=108和中子N=162存在变形壳,在质子Z=114和中子N=184存在球形壳.用得到的α衰变能和Viola Seaborg公式估算了α衰变半寿命,能合理地符合实验测量值. The groundstate properties of superheavy nuclei are investigated using the SkyrmeHartreeFock model. The pairing correlation is treated by the BCS method with the pairing δ force. Binding energies, α decays, spontaneous fissions, shell structures and deformations are discussed. Our calculations reproduce experimential binding energies and α decay energies.It is found that superheavy nuclei can be grouped with two kinds of deformations: i) well deformed prolate shapes (β2≈0.2) around 270108...
用Skyrme Hartree Fock+BCS方法计算了超重核的基态性质,讨论了结合能、α衰变、形变、壳结构和自发裂变等问题.计算得到的结合能较好地反映了实验测量值,α衰变能与实验值符合很好.发现基本上有两种类型的超重核形变:在270108核附近的β2≈0.2的长椭球形变和在298114核附近的近球形形变.单粒子能级分布计算表明:在质子Z=108和中子N=162存在变形壳,在质子Z=114和中子N=184存在球形壳.用得到的α衰变能和Viola Seaborg公式估算了α衰变半寿命,能合理地符合实验测量值. The groundstate properties of superheavy nuclei are investigated using the SkyrmeHartreeFock model. The pairing correlation is treated by the BCS method with the pairing δ force. Binding energies, α decays, spontaneous fissions, shell structures and deformations are discussed. Our calculations reproduce experimential binding energies and α decay energies.It is found that superheavy nuclei can be grouped with two kinds of deformations: i) well deformed prolate shapes (β2≈0.2) around 270108...
2003, 20(2): 121-131.
doi: 10.11804/NuclPhysRev.20.02.121
摘要:
发展了一种改进的量子分子动力学模型,并用这一模型研究了40,48Ca+90,96Zr的近垒熔合反应.改进的量子分子动力学模型能很好地描述一系列核,从6Li到208Pb,的基态性质及它们的时间演化.在相同参数下计算得到的40Ca+90Zr以及40Ca+96Zr这两个熔合反应的激发函数与实验结果都符合得相当好.在分析丰中子核熔合截面增强机制中,发现丰中子核熔合反应初始阶段颈部的N/Z值明显偏大,促使反应中动态位垒降低,从而引起了丰中子核反应熔合截面的增强. An improved Quantum Molecular Dynamics (QMD) model is proposed and the fusion reactions 40, 48Ca+90, 96Zr are studied by using this model. With our improved QMD model, the ground state properties and their time evolution of nuclei from 6Li to 208Pb can be reproduced reasonably well and the excitation functions of fusion cross section for reactions40Ca+96Zr and 40Ca+96Zr at near barrier can be reproduced remarkably well with the same set of parameters...
发展了一种改进的量子分子动力学模型,并用这一模型研究了40,48Ca+90,96Zr的近垒熔合反应.改进的量子分子动力学模型能很好地描述一系列核,从6Li到208Pb,的基态性质及它们的时间演化.在相同参数下计算得到的40Ca+90Zr以及40Ca+96Zr这两个熔合反应的激发函数与实验结果都符合得相当好.在分析丰中子核熔合截面增强机制中,发现丰中子核熔合反应初始阶段颈部的N/Z值明显偏大,促使反应中动态位垒降低,从而引起了丰中子核反应熔合截面的增强. An improved Quantum Molecular Dynamics (QMD) model is proposed and the fusion reactions 40, 48Ca+90, 96Zr are studied by using this model. With our improved QMD model, the ground state properties and their time evolution of nuclei from 6Li to 208Pb can be reproduced reasonably well and the excitation functions of fusion cross section for reactions40Ca+96Zr and 40Ca+96Zr at near barrier can be reproduced remarkably well with the same set of parameters...
2003, 20(2): 132-136.
doi: 10.11804/NuclPhysRev.20.02.132
摘要:
用双中心核态参数描写重核熔合过程,以一个布朗粒子通过二次势位垒的简化模型得到了熔合几率的解析表达式.在两碰撞核的接触处,颈部变量的变化遵守高斯分布,而沿拉长方向的初始平均动能由表面摩擦模型所确定.计算了几个对称和近似对称的反应系统的熔合激发函数,并与实验结果进行了比较.讨论了颈部增长和初始能量损失对熔合障碍产生的效应. Dissipative dynamics of fusion of massive nuclei is studied in terms of the twocenter shape parameterization. Fusion probability is obtained analytically from a Brownian particle passing over a parabolic potential barrier along the elongation coordinate. The neck variable at the initial contact shape is supposed to be a Gaussian distribution. Fusion probabilities of several symmetric or nearly symmetric systems in central collisions are calculatedand compared with experimental data. Effects of neck folding...
用双中心核态参数描写重核熔合过程,以一个布朗粒子通过二次势位垒的简化模型得到了熔合几率的解析表达式.在两碰撞核的接触处,颈部变量的变化遵守高斯分布,而沿拉长方向的初始平均动能由表面摩擦模型所确定.计算了几个对称和近似对称的反应系统的熔合激发函数,并与实验结果进行了比较.讨论了颈部增长和初始能量损失对熔合障碍产生的效应. Dissipative dynamics of fusion of massive nuclei is studied in terms of the twocenter shape parameterization. Fusion probability is obtained analytically from a Brownian particle passing over a parabolic potential barrier along the elongation coordinate. The neck variable at the initial contact shape is supposed to be a Gaussian distribution. Fusion probabilities of several symmetric or nearly symmetric systems in central collisions are calculatedand compared with experimental data. Effects of neck folding...
2003, 20(2): 137-147.
doi: 10.11804/NuclPhysRev.20.02.137
摘要:
总结和回顾了超重核结构和反应研究的历史和现状,利用形变约束的相对论平均场理论系统计算了实验观测到的Z=102—112号元素的能量随形变的变化,得到了这些核素的基态和鞍点性质,利用Strutinsky壳修正方法研究了壳效应对这些核素的影响.利用所得到的结构信息,计算了相应的冷熔合反应的截面,给出了与实验相仿的结果,得到Z=118号元素的合成截面为23pb,比宏观模型的结果小20倍.讨论了相关物理量对反应截面的影响.同时,还给出了相对论连续谱Hartree Bogoliubov(RCHB)理论对滴线外核1800Sn的描述. The studieson structure and reaction for superheavy elements are reviewed. Based on constrained relativistic mean field(CRMF) theory, binding energiesof elements from Z=102 to Z=112, which can be measured experimentally, as a function of deformation arecalculated, and the properties of equilibrium and saddle point of these nuclides are obtained. Using the single particle levels based on CRMF, the shell effects are obtained with Structinsky method. The cross sections of the cold fusion are est...
总结和回顾了超重核结构和反应研究的历史和现状,利用形变约束的相对论平均场理论系统计算了实验观测到的Z=102—112号元素的能量随形变的变化,得到了这些核素的基态和鞍点性质,利用Strutinsky壳修正方法研究了壳效应对这些核素的影响.利用所得到的结构信息,计算了相应的冷熔合反应的截面,给出了与实验相仿的结果,得到Z=118号元素的合成截面为23pb,比宏观模型的结果小20倍.讨论了相关物理量对反应截面的影响.同时,还给出了相对论连续谱Hartree Bogoliubov(RCHB)理论对滴线外核1800Sn的描述. The studieson structure and reaction for superheavy elements are reviewed. Based on constrained relativistic mean field(CRMF) theory, binding energiesof elements from Z=102 to Z=112, which can be measured experimentally, as a function of deformation arecalculated, and the properties of equilibrium and saddle point of these nuclides are obtained. Using the single particle levels based on CRMF, the shell effects are obtained with Structinsky method. The cross sections of the cold fusion are est...
2003, 20(2): 148-153.
doi: 10.11804/NuclPhysRev.20.02.148
摘要:
研究了基于双核模型的粒子交换势能面.原子核的形变效应对于势能面的形状有较大的影响.在反应过程中,作为反应时间函数的动态形变的变化是显著的.通过求解主方程,对一些基于冷熔合机制的反应道的全熔合几率也进行了讨论. The Potential Energy Surface (PES) for particle exchange in Dinuclear system is studied in detail. It is found that the nuclear deformation effect can change the shape of PES significantly. The dynamical deformation as a function of the reaction time in the reaction process is investigated in a simple model and we found that its variation with time is dramatic. The fusion probabilities P-CN of some reaction channels based on the mechanism of cold fusion are also calculated.
研究了基于双核模型的粒子交换势能面.原子核的形变效应对于势能面的形状有较大的影响.在反应过程中,作为反应时间函数的动态形变的变化是显著的.通过求解主方程,对一些基于冷熔合机制的反应道的全熔合几率也进行了讨论. The Potential Energy Surface (PES) for particle exchange in Dinuclear system is studied in detail. It is found that the nuclear deformation effect can change the shape of PES significantly. The dynamical deformation as a function of the reaction time in the reaction process is investigated in a simple model and we found that its variation with time is dramatic. The fusion probabilities P-CN of some reaction channels based on the mechanism of cold fusion are also calculated.
2003, 20(2): 154-159.
doi: 10.11804/NuclPhysRev.20.02.154
摘要:
在形变的相对论平均场模型下采用NL Z2,TMA两套参数对一些偶 偶核基态性质进行了系统的计算,并将理论计算的结合能、α衰变能与已知的实验数据进行了对比分析.结果发现两方面的数据能够比较好地吻合,从而验证了相对论平均场模型对超重核研究是可行的.同时在计算中给出了未知核素基态性质的计算结果,可供以后在理论或实验上研究超重核时参考. The ground state properties of the eveneven nuclei with proton number Z=94-104 have been systematically calculated in the deformed relativistic meanfield (RMF) theory with two sets of force parameters, TMA and NL Z2. Comparing the calculated binding energies and alphadecay energys with the experimental ones, it is found that theoretical results are in good agreement with experimental data. The reliability of the RMF model for eveneven superheavy nuclei has been tested by this comparison...
在形变的相对论平均场模型下采用NL Z2,TMA两套参数对一些偶 偶核基态性质进行了系统的计算,并将理论计算的结合能、α衰变能与已知的实验数据进行了对比分析.结果发现两方面的数据能够比较好地吻合,从而验证了相对论平均场模型对超重核研究是可行的.同时在计算中给出了未知核素基态性质的计算结果,可供以后在理论或实验上研究超重核时参考. The ground state properties of the eveneven nuclei with proton number Z=94-104 have been systematically calculated in the deformed relativistic meanfield (RMF) theory with two sets of force parameters, TMA and NL Z2. Comparing the calculated binding energies and alphadecay energys with the experimental ones, it is found that theoretical results are in good agreement with experimental data. The reliability of the RMF model for eveneven superheavy nuclei has been tested by this comparison...
2003, 20(2): 160-164.
doi: 10.11804/NuclPhysRev.20.02.160
摘要:
计算了以208Pb为靶的一系列重离子熔合反应双核系统核子转移驱动势.它制约由输运方程所支配的核子转移速率,因而确定了双核系统形成复合核的几率.并由此可确定形成复合核所必须的最低激发能,即形成最稳定复合核的最佳激发能,得到了与已知实验值基本符合的结果. Particle transfer driven potentials in Di nuclear System (DNS) in heavy ion collisions based on 208Pb target are calculated. The driven potential controls the particle transfer velocity in the process governed by the diffusion equation, and as a consequence determines the compound nuclear formation probability of DNS. The minimum excitation energy to form a compound nucleus, which is the optimum excitation energy to form the most stable compound nucleus, has been calculated, and the results are basica...
计算了以208Pb为靶的一系列重离子熔合反应双核系统核子转移驱动势.它制约由输运方程所支配的核子转移速率,因而确定了双核系统形成复合核的几率.并由此可确定形成复合核所必须的最低激发能,即形成最稳定复合核的最佳激发能,得到了与已知实验值基本符合的结果. Particle transfer driven potentials in Di nuclear System (DNS) in heavy ion collisions based on 208Pb target are calculated. The driven potential controls the particle transfer velocity in the process governed by the diffusion equation, and as a consequence determines the compound nuclear formation probability of DNS. The minimum excitation energy to form a compound nucleus, which is the optimum excitation energy to form the most stable compound nucleus, has been calculated, and the results are basica...
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