Studies of new inorganic species using relativistic quantum chemistry

In the present work the methods of relativistic quantum chemistry have been applied to a number of small systems containing heavy elements, for which relativistic effects are important. First, a thorough introduction of the methods used is presented. This includes some of the general methods of computational chemistry and a special section dealing with how to include the effects of relativity in quantum chemical calculations. Second, after this introduction the results obtained are presented. Investigations on high-valent mercury compounds are presented and new ways to synthesise such compounds are proposed. The methods described were applied to certain systems containing short Pt-Tl contacts. It was possible to explain the interesting bonding situation in these compounds. One of the most common actinide compounds, uranium hexafluoride was investigated and a new picture of the bonding was presented. Furthermore the rareness of uranium-cyanide compounds was discussed. In a foray into the chemistry of gold, well known for its strong relativistic effects, investigations on different gold systems were performed. Analogies between Au$^+$ and platinum on one hand and oxygen on the other were found. New systems with multiple bonds to gold were proposed to experimentalists. One of the proposed systems was spectroscopically observed shortly afterwards. A very interesting molecule, which was theoretically predicted a few years ago is WAu$_{12}$. Some of its properties were calculated and the bonding situation was discussed. In a further study on gold compounds it was possible to explain the substitution pattern in bis[phosphane-gold(I)] thiocyanate complexes. This is of some help to experimentalists as the systems could not be crystallised and the structure was therefore unknown. Finally, computations on one of the heaviest elements in the periodic table were performed. Calculation on compounds containing element 110, darmstadtium, showed that it behaves similarly as its lighter homologue platinum. The extreme importance of relativistic effects for these systems was also shown.

Nucleosynthesis in the accretion disks of type II collapsars

We investigate nucleosynthesis inside the gamma-ray burst (GRB) accretion disks formed by the Type II collapsars. In these collapsars, the core collapse of massive stars first leads to the formation of a proto-neutron star. After that, an outward moving shock triggers a successful supernova. However, the supernova ejecta lacks momentum and within a few seconds the newly formed neutron star gets transformed to a stellar mass black hole via massive fallback. The hydrodynamics of such an accretion disk formed from the fallback material of the supernova ejecta has been studied extensively in the past. We use these well-established hydrodynamic models for our accretion disk in order to understand nucleosynthesis, which is mainly advection dominated in the outer regions. Neutrino cooling becomes important in the inner disk where the temperature and density are higher. The higher the accretion rate (M) over dot is, the higher the density and temperature are in the disks. We deal with accretion disks with relatively low accretion rates: 0.001 M-circle dot s(-1) less than or similar to (M) over dot less than or similar to 0.01 M-circle dot s(-1) and hence these disks are predominantly advection dominated. We use He-rich and Si-rich abundances as the initial condition of nucleosynthesis at the outer disk, and being equipped with the disk hydrodynamics and the nuclear network code, we study the abundance evolution as matter inflows and falls into the central object. We investigate the variation in the nucleosynthesis products in the disk with the change in the initial abundance at the outer disk and also with the change in the mass accretion rate. We report the synthesis of several unusual nuclei like P-31, K-39, Sc-43, Cl-35 and various isotopes of titanium, vanadium, chromium, manganese and copper. We also confirm that isotopes of iron, cobalt, nickel, argon, calcium, sulphur and silicon get synthesized in the disk, as shown by previous authors. Much of these heavy elements thus synthesized are ejected from the disk via outflows and hence they should leave their signature in observed data.

Nucleosynthesis in the outflows associated with accretion disks of type II collapsars

We investigate nucleosynthesis inside the outflows from gamma-ray burst (GRB) accretion disks formed by the Type II collapsars. In these collapsars, massive stars undergo core collapse to form a proto-neutron star initially, and a mild supernova (SN) explosion is driven. The SN ejecta lack momentum, and subsequently this newly formed neutron star gets transformed to a stellar mass black hole via massive fallback. The hydrodynamics and the nucleosynthesis in these accretion disks have been studied extensively in the past. Several heavy elements are synthesized in the disk, and much of these heavy elements are ejected from the disk via winds and outflows. We study nucleosynthesis in the outflows launched from these disks by using an adiabatic, spherically expanding outflow model, to understand which of these elements thus synthesized in the disk survive in the outflow. While studying this, we find that many new elements like isotopes of titanium, copper, zinc, etc., are present in the outflows. Ni-56 is abundantly synthesized in most of the cases in the outflow, which implies that the outflows from these disks in a majority of cases will lead to an observable SN explosion. It is mainly present when outflow is considered from the He-rich, Ni-56/Fe-54-rich zones of the disks. However, outflow from the Si-rich zone of the disk remains rich in silicon. Although emission lines of many of these heavy elements have been observed in the X-ray afterglows of several GRBs by Chandra, BeppoSAX, XMM-Newton, etc., Swift seems to have not yet detected these lines.

Simulation of the Lanzhou Penning Trap LPT

The LPT (Lanzhou Penning Trap) is under construction and its task is to perforin direct mass measurement of fusion-evaporation residue, and if possible for heavy isotopes. Detailed simulations have been clone for a good understanding to the ion's movement and mechanics in the trap. The optimizal ion of the LPT is also performed based on the simulation. With a scale of 0.5 mm per grid used in the, simulation and many other limitations a highest mass resolution has been achieved to be 1.9 x 10(-5). An unexpected behavioin in the simulation related to magnetron motion has been found.

Neutron and proton diffusion in fusion reactions for the synthesis of superheavy nuclei

The restriction of the one dimensional (1D) master equation (ME) with the mass number of the projectile-like fragment as a variable is studied, and a two-dimensional (2D) master equation with the neutron and proton numbers as independent variables is set up, and solved numerically. Our study showed that the 2D ME can describe the fusion process well in all projectile-target combinations. Therefore the possible channels to synthesize super-heavy nuclei can be studied correctly in wider possibilities. The available condition for employing 1D ME is pointed out.

High precision mass measurement and LPT

A Penning trap, which can measure the atomic masses with the highest precision, is one of the most important facilities in nuclear physics research nowadays. The precision mass data play an important role in the studies of nuclear models, mass formulas, nuclear synthesis processes in the nuclear astrophysics, symmetries of the weak interaction and the conserved vector current (CVC) hypothesis. The status of high precision mass measurement around the world, the basic principle of Penning trap and the basic information about the LPT (Lanzhou Penning Trap) are introduced.

Latest progress of the RFQ cooler and buncher RFQ1L

The RFQ cooler and buncher RFQ1L is a key device of the SHANS (Spectrometer for Heavy Atoms and Nucleax Structure). The status of the machining and assembly of the central part is introduced, and the structure of the whole RFQ1L system and the preliminary plan for the testing are discussed also.

Experimental study of the high-voltage breakdown and simulations for the RFQ cooler and buncher RFQ1L

The RFQ cooler and buncher RFQ1L is one of the key parts of the being-built super-heavy nuclide research spectrometer. In order to understand the high-voltage breakdown phenomenon, the voltages between electrodes have been measured. In addition, more extensive simulations have been performed for better understanding and optimizing the RFQ1L work points.

超重核合成机制—包含中子、质子跃迁的二维主方程

用双核模型研究超重核的合成机制，最主要的部分是由双核系统演化到复合核的熔合机制研究。双核模型认为超重复合核的形成是由弹核的核子全部转移到靶核所致。核子分中子和质子，在以前的研究中，描述熔合过程的主方程是一维的，以类弹核的质量数 为变量，与此对应的驱动势也是一维的。对确定的 ，其同位旋的确定是由较低的势能面确定的，这样确定的同位旋与反应系统的同位旋很接近。但是我们的研究发现，对入射道同位旋与复合系统同位旋相差较大的情况，入射道在双核系统势能面比较高的位置，有时甚至在最高位置，这时核子转移的同位旋路径比较复杂，以致一维主方程的描述给出错误的结果。为此，建立了以类弹碎片中子数 和质子数 为变量的二维主方程，并建立了二维主方程的分步差分的解法，完成了解二维主方程的程序编写。并对一些典型的弹核、靶核同位旋与复合系统同位旋相差较大的系统进行了研究。对这些反应道的研究表明，无论1D主方程对这些反应道的蒸发剩余截面的研究给出了过高、或过低的估计，2D主方程都能给出与实验值一致地结果。二维主方程适用于所有的弹靶组合入射道。对确定的超重核目标，可以较准确的对各种弹靶组合的合成几率给出预言，特别是研究合成超重核的同位素依赖性，因而极大增加了预言合成预期超重岛区域超重核的弹靶组合的选择性。本工作还检验了一维主方程的适用条件：入射点必须在比较接近二维驱动势谷底时才适用，这时一维主方程预言的蒸发剩余截面的结果与二维主方程的结果很接近

超重谱仪中冷却聚束器RFQ1L的模拟研究

对超重核和超重元素越来越多的探索和研究，以及对远离β稳定线奇异核的精细研究，都迫切地需要低能量、高品质的放射性束流。然而，由原子核反应产生的放射性束流普遍具有能量分散大、发射度大以及束流斑点大的缺点，因此，对放射性次级束流进行进一步的操控成为深入研究的必需条件。充有缓冲气体的RFQ冷却聚束器是适合这项任务的最佳选择。它不但可以高速度、高效率地提高束流的品质，而且适用于所有的核素。这项技术在上世纪末蓬勃地发展起来，现在已经成为世界各主要实验室进行放射性次级束流操控的必备实验装置。在中国科学院近代物理研究所，一台正在研制的专用于研究长寿命核素的超重核研究谱仪中就使用了RFQ冷却聚束器来冷却、约束和储存离子。论文首先简单介绍了近代物理研究所超重谱仪的情况和国际上RFQ冷却聚束器的研究情况，其次阐述了RFQ冷却聚束器相关原理，然后重点论述了用SIMION程序进行模拟的方法和对RFQ1L冷却段的模拟情况，并对模拟结果进行了讨论，接着，讨论了计算机无法模拟的一些因素，重点讨论了气体击穿问题，最后，对本论文的工作进行了总结，并对下一步工作进行了展望望。对RFQ1L冷却段的模拟和气体击穿问题是本论文的两个重点。冷却段的模拟是以为例进行的。通过改变缓冲气体压强、入射离子能量以及轴向电场梯度，得到了离子在RFQ冷却聚束器中不同的运动情况，得到了一些有意义的结论，有助于设备的设计和工作点的选择。另外，RFQ冷却聚束器的工作区域，正好位于缓冲气体最容易被击穿的范围，再加上射频的影响，因此气体击穿问题成为制约工作点选择的一个非常重要的因素。本文对此也作了详细的讨论

基于RIBLL束线开展超重核合成的可行性研究

超重元素合成研究是当今国际上核物理研究的热点领域之一，也是中国科学院近代物理研究所的一个重要研究方向。根据实际情况，我们确定了两步走的发展方案。针对第一步发展方案，我们对RIBLL放射性束流线进行了改造。具体做法就是在RIBLL入口的前段增加一个速度选择器，并将原束流传输线的前半段改造为充气谱仪。本论文详细论述了RIBLL改造所涉及到的硬件设计和建造以及改造后系统的各项性能测试。硬件部分主要包括反应靶室、转靶系统、速度选择器、充气及气压控制系统、焦平面的衰变探测器等。性能测试方面主要开展了以下工作：(1) 利用放射源对速度选择器的接收立体角和动量接收度进行了测试；(2) 测量了铀离子经不同厚度碳膜后的电荷态分布，并与经验公式计算进行了比较；(3) 利用已知截面的反应道和靶反冲核分别对系统的传输效率、充气谱仪的最佳气压值和重离子在氦气中的平衡电荷态进行了研究。基于以上测试的结果，论文对在改造后的RIBLL上开展超重核合成研究的可行性进行了讨论。结论是由于RIBLL的二极磁铁的分析能力太强，大大降低了系统的传输效率，因此该谱仪只可用于原子序数Z≤107的超重核合成研究和生成截面较高的短寿命滴线核的合成及性质研究，对于更高原子序数的超重核合成研究应该放到正在建造的SHANS谱议上进行

超重核合成机制—包含中子、质子跃迁的二维主方程

用双核模型研究超重核的合成机制，最主要的部分是由双核系统演化到复合核的熔合机制研究。双核模型认为超重复合核的形成是由弹核的核子全部转移到靶核所致。核子分中子和质子，在以前的研究中，描述熔合过程的主方程是一维的，以类弹核的质量数 为变量，与此对应的驱动势也是一维的。对确定的 ，其同位旋的确定是由较低的势能面确定的，这样确定的同位旋与反应系统的同位旋很接近。但是我们的研究发现，对入射道同位旋与复合系统同位旋相差较大的情况，入射道在双核系统势能面比较高的位置，有时甚至在最高位置，这时核子转移的同位旋路径比较复杂，以致一维主方程的描述给出错误的结果。为此，建立了以类弹碎片中子数 和质子数 为变量的二维主方程，并建立了二维主方程的分步差分的解法，完成了解二维主方程的程序编写。并对一些典型的弹核、靶核同位旋与复合系统同位旋相差较大的系统进行了研究。对这些反应道的研究表明，无论1D主方程对这些反应道的蒸发剩余截面的研究给出了过高、或过低的估计，2D主方程都能给出与实验值一致地结果。二维主方程适用于所有的弹靶组合入射道。对确定的超重核目标，可以较准确的对各种弹靶组合的合成几率给出预言，特别是研究合成超重核的同位素依赖性，因而极大增加了预言合成预期超重岛区域超重核的弹靶组合的选择性。本工作还检验了一维主方程的适用条件：入射点必须在比较接近二维驱动势谷底时才适用，这时一维主方程预言的蒸发剩余截面的结果与二维主方程的结果很接近

SYNTHESIS AND CHARACTERIZATION OF POLYMER-SUPPORTED LANTHANIDE COMPLEXES AND BUTADIENE POLYMERIZATION BASED ON THEM

Poly(styrene-acrylic acid)-lanthanide (Ln.PSAA) and poly(ethylene-acrylic acid)-neodymium (NdPEAA) complexes have been prepared and characterized. The infrared and X-ray photoelectron spectra indicate that the lanthanide complexes possess the bidentate carboxylate structure Ln-O-C(R)-O (see structure B in text). The catalytic behavior of the complexes has been described. The catalytic activities of Nd.PSAA and Nd.PEAA are much greater than that of the corresponding low molecular weight catalyst for butadiene polymerization. The activities of various individual lanthanide elements are quite different from one another. Neodymium shows the highest activity. Europium, samarium and the heavy elements exhibit very low or no activities. The cis-1,4 content of the polybutadiene obtained is not affected by different lanthanide elements in the series. The complex with the intermediate content of the functional group has a higher activity than the others. The polymer-supported lanthanide complexes having different constitutions have different catalytic activities. When the molar ratio of lanthanide to the functional group is ca. 0.2, the activity of the complex is in the optimum state. The activity is influenced by the dispersion of the lanthanide metal immobilized on the polymer chain. Catalytic activity can be improved by adding other metals to the catalyst system.