自然界中超重元素的寻找方法

六十年代末理论物理学家预言,在周期表中原子序数Z为110至126的空位上存在着一个新的稳定岛。自那时以来,世界上不少国家的科学工作者试图在自然界中寻找这类越重元素,发表了近百篇的有关文献,至于自然界中是否确实存在超重元素,目前还没有定论,研究工作仍在继续进行中。 研究超重元素具有重要的理论意义,如果发现了这类元素,对于阐明核结构的基本问题极为重要,并能提供周期表中元素存在边界的新信息。甚至还有人认为超重元素可能是一类新的能源材料。     

超重元素Sg的液相化学条件实验——Mo和W的萃取色谱行为

通过对超重元素Sg的同族元素Mo和W在负载有萃取剂α-安息香肟的聚四氟乙烯载体上进行吸附实验,为利用萃取色谱法在线研究超重元素Sg的液相化学行为提供基础。实验结果发现,在一定的酸度条件下,Mo和W的最大吸附率可分别达到92%和87%,且Mo的吸附动力学较W快。在混合酸体系HF/HNO3中,由于Mo和W与阴离子F-形成化合物的能力不同,导致它们的吸附行为有明显的差别,这为比较超重元素Sg的化学行为提供了很好的条件。同时,温度对Mo和W的吸附分配系数有一定的影响,随着温度的升高,它们的吸附效率都有所减小,但Mo和W在负载有萃取剂α-安息香肟的聚四氟乙烯载体上的吸附行为是自发进行的。     

超重元素合成实验靶室及转靶装置

文章介绍兰州重离子加速器放射性次级束流线（RIBLL）的超重元素合成实验靶室和转靶系统，并对改进的真空密封磁耦合传动机械作简单描述。转靶系统采用可程序控制的无级变速电机、真空密[JP2]封磁流体耦合和特殊皮带传动机构，使得靶盘转速在0~600r/min范围内可调，靶盘边缘摆幅＜0.2mm。     

科学家发现最新的超重元素：第118号元素

[本刊2006年11月综合报道]据有关媒体2006年10月17日报道,来自俄罗斯和美国的研究人员10月15日宣布,他们已经制造出了一种新的超重元素,原子序号为第118号的元素。     

气相色谱过程的蒙特卡罗模拟

用蒙特卡罗方法模拟了易挥发化合物的气相色谱微观动力学行为,描述了化合物随气流在固体色谱柱表面的迁移以及吸附-解吸等过程.按气相色谱微观动力学模型编译的计算机程序模拟了超重元素化合物在等温色谱及热色谱的动力学过程,并根据不同实验条件进行了大量计算.计算结果与实验数据较为吻合.讨论了超重元素的半衰期、吸附态的周期、载气流量以及化合物的质量密度等对实验结果的影响及该理论模型的优点和待改进的地方.     

状态方程靶的纳米胶连复合技术研究

为了模拟和解释材料在激光冲击产生的高应变率和压力下的实验现象,物理实验对状态方程实验靶多层材料之间的胶层厚度提出了亚微米级的需求。针对现有复合方法的不足,本文采用引发式化学气相沉积方法制备固体原胶薄膜,并采用液相活化方法对原胶薄膜进行活化和固化,实现了状态方程实验靶的亚微米级无损胶连复合。采用多种表征技术对纳米胶连复合样品的胶层厚度及形貌进行表征,胶层厚度为亚微米级,最薄时仅300 nm。本文所报道的纳米胶连复合方法能为激光加载压缩物理实验的精度提高和实验结果的准确解释提供制靶技术保障。     

N,N,N',N'-四丁基-3-氧-戊二酰胺辐解产物研究Ⅰ.二丁胺的定性和定量分析

采用红外、顶空固相微萃取-气相色谱/质谱联用的方法,研究了萃取剂N,N,N',N'-四丁基-3-氧-戊二酰胺(TBOPDA)的液相辐解产物,并通过与标准物质对照,确定TBOPDA的液相辐解产物中存在二丁胺和N,N-二正丁基甲酰胺.采用高效液相色谱、固相微萃取-气相色谱联用方法,定量分析了在辐照过程中TBOPDA的分解情况和二丁胺的产生情况,分别计算了两者的产额.提出了TBOPDA的3种可能断裂方式.     

N,N,N’,N’-四丁基-3-氧-戊二酰胺辐解产物研究 Ⅰ.二丁胺的定性和定量分析

采用红外、顶空固相微萃取-气相色谱／质谱联用的方法，研究了萃取剂N，N，N'，N'-四丁基-3-氧-戊二酰胺(TBOPDA)的液相辐解产物，并通过与标准物质对照，确定TBOPDA的液相辐解产物中存在二丁胺和N，N-二正丁基甲酰胺。采用高效液相色谱、固相微萃取-气相色谱联用方法，定量分析了在辐照过程中TBOPDA的分解情况和二丁胺的产生情况，分别计算了两者的产额。提出了TBOPDA的3种可能断裂方式。     

Q-Value Effects on Production of Superheavy Nuclei

The yields of superheavy nucleus ^270Hs via 4n evaporation channel of fusion reactions ^26Mg＋^248Cm, ^30Si＋^244Pu, ^36S＋^238U and ^48Ca＋^226Ra are studied using a two-parameter Smoluchowski equation.     

Statistical Behavoirs of Quantum Spectra in Superheavy Nuclei

From the point of view of the interplay between order and chaos, the most regular single-particle motion of neutrons has been found in the superheavy system of Z=120 and N=184 based on the Skyrme-Hartree-Fock model and in the system of Z=120 and N=12 based on the relativistic mean-field model. It has been shown that the statistical analysis of spectra indeed can give very valuable information about the stability of superheavy systems. The significance of this kind of study can go far beyond the investigation on the stability of superheavy systems and it may give a deep     

Superheavy quasi-atoms and quantum electrodynamics in strong fields

Distinct peak structures have been observed in spectra of positrons emitted in collisions of very heavy ions such as U-Th, U-U, Th-Cm and U-Cm. Characteristic features of these structures are discussed and confronted with our theoretical results. It is argued that this experimental finding could be associated with the spontaneous positron emission in the strong Coulomb field of giant nuclear molecules.     

Superheavy Fragments Produced in Asymmetric Strongly Damped Collisions

In recent years, a great achievement in synthesis of superheavy elements （SHEs） has been made by the complete fusion reactions. However, the further experimental extension of the region of SHEs to the central area of ＂Island of Stability＂ by means of those reactions is limited by the number of neutron available of projectiles and targets, and also by the very low production cross section. In order to search new superheavy nuclei the radioactive ion beam will have to be utilized, but up to now the intensive radioactive ion beam is not available. An alternatively possible pathway to production of superheavy elements is the strongly damped reaction between two very heavy nuclei.     

Origin of Unexpected Isotopic Trends in Synthesis of Superheavy Nuclei

Synthesis of the superheavy elements （SHE） is a topic of great interest in nuclear physics. Up to now the region of the ＂island of superheavy nucleus＂ is extended up to element Z= 118 using the 48Ca-induced hot fusion reactions with actinide targets. However, the superheavy nuclei synthesized nowadays are all in the proton-rich side of the ＂superheavy island＂. In order to reach the center region of the ＂island of superheavy nucleus＂,     

Optimal Reactions for Synthesis of Superheavy Nucleus ^270Hs

The macroscopic-microscopic approach predicts a strong proton-deformed shell at Z=108 to be a partner for the neutron shell at N=162. Thus the nucleus ^270Hs is expected to be a relatively strongly bound ＂double-magic＂ deformed nucleus. Therefore, it is of great interest to synthesize the nucleus 27~Hs and to investigate its structure experimentally. However,     

弥散型燃料等效弹性性质的有限元模拟

弥散型核燃料元件在反应堆中的安全和可靠性与元件芯体的等效力学性能密切相关.本研究采用细观力学的方法,假设芯体中的燃料颗粒在基体中周期性排列,从中取出代表性体积元,运用有限元方法计算弥散型燃料在不同温度和颗粒体积含量下的等效弹性模量.分析比较了颗粒的体积含量和分布形式对弥散型燃料等效弹性性质的影响,并在颗粒随机排列时,将...     

Numerical Simulation for Chemical Reactions of Actinide Elements in Aqueous Nitric Acid Solution

A computer code REACT incorporating 30 rate equations of reactions, i.e. radiolytic formation and decomposition of HNO₂, redox and disproportionation reactions, was developed to simulate behavior of actinide elements in the aqueous nitric acid solution. Main aspects of REACT code were explained briefly and then calculated results were compared with reported data to evaluate the model in the systems of radiolytic accumulation of HNO₂, stabilization process of Pu solution. The study showed that some radiolytic products other than HNO₂ would play a significant role and should be taken into account for precise simulation of very slow valency change of Pu in the neat Pu solution particularly with high radiation power density. Some examples of calculation were also shown for systems of reduction of Pp and Np by uranous or HAN and oxidation of Np (V) to Np (VI).     

Applications of Skyrme Energy-Density Functional to Fusion Reactions for Synthesis of Superheavy Nuclei

The Skyrme energy-density functional approach has been extended to study the massive heavy ion fusion reactions. Based on the fusion barrier obtained and the parameterized barrier distribution the fusion （capture） excitation functions of a lot of heavy-ion fusion reactions are studied systematically.