丰中子核~6He在~(28)Si靶上的反应总截面测量

实验测量了20—40MeV u的轻丰中子核6He在Si靶上的反应总截面,并且结合6He的高能实验数据,采用双参数HO密度分布形式用Glauber模型计算得到较好的拟合.与Warner的实验数据比较,反应总截面数据系统性好,并与能量有明显的依赖关系.

28.7MeV/u的~(14,16,18)O+~(7,9)Be反应中的同位素分布研究

用同位旋相关的Boltzmann Langevin方程研究了在入射能量为2 8 7MeV/u下 ,不同弹核 14O ,16 O和 18O轰击不同靶核 7Be和 9Be的反应 ,计算了生成碎片的产生截面 ,发现用丰中子 (缺中子 )炮弹或丰中子 (缺中子 )靶进行反应 ,所得到的产物均有丰中子 (缺中子 )的碎片出现 .同位素分布宽度和峰位与入射体系密切相关 ,产生碎片的电荷数越接近入射弹核的电荷数 ,则同位素分布的宽度越大 ,峰位偏离β稳定线值越远 ,其同位旋效应越明显 .

质子滴线核~(12)N在~(28)Si靶上的核反应总截面测量

描述了 5 0 .4MeV/u的12 N和 42 .3MeV/u的13 N次级放射性束在2 8Si靶上引起的核反应总截面σr 实验研究 ,结果发现12 N的反应总截面σr 比其相邻同位素核13 N有着异常的增大 .这可能是核形变及核子对效应造成的 ,试验中的测量误差也不可忽视 .利用微观Glauber模型计算了12 N在2 8Si靶上的核反应总截面 ,并与实验结果做了比较 ,发现理论计算与实验结果拟合较好

~(28)Si+~(12)C中的两体反应与全熔合反应

利用ΔE E望远镜系统测量了 1 56 3MeV2 8Si+ 12 C反应 (近对称系统 )中出射的Z =4— 1 4的产物元素的能谱和角分布 ,并由此给出了这些产物的胁变截面图 .从理论上计算了Z =4— 1 1产物的实验室系最可几动能分布E1(θ)和各元素的质心系的总动能分布Et(Z) ,指出了这些产物主要来自系统的两体反应过程 .还给出了该反应系统的全熔合截面值为 (980± 68)mb ,并指出从低能数据外推到此能量下的全熔合截面值与实验值之差主要归因于两体过程 .

Measurement of total reaction cross section for neutron-rich nucleus Li-11 on Si-28 target at medium energy

The neutron-rich nucleus Li-11 is separated by the radioactive ion beam line RIBLL at HIRFL from the breakup of 50MeV/u C-13 on Be target. The total reaction cross sections for Li-11 at energies range from 25 to 45MeV/u on Si target have been measured by using the transmission method. The experimental data at high and low energies can be fitted well by Glauber model using two Gauss density distribution. The matter radius of Li-11 was also deduced.

Investigation of two-proton emission from excited states of the odd-Z nucleus P-28 by complete-kinematics measurements

An experiment to study exotic two-proton emission from excited levels of the odd-Z nucleus P-28 was performed at the National Laboratory of Heavy Ion Research-Radioactive Ion Beam Line (HIRFL-RIBLL) facility. The projectile P-28 at the energy of 46.5 MeV/u was bombarding a Au-197 target to populate the excited states via Coulomb excitation. Complete-kinematics measurements were realized by the array of silicon strip detectors and the CsI + PIN telescope. Two-proton events were selected and the relativistic-kinematics reconstruction was carried out. The spectrum of relative momentum and opening angle between two protons was deduced from Monte Carlo simulations. Experimental results show that two-proton emission from P-28 excited states less than 17.0 MeV is mainly two-body sequential emission or three-body simultaneous decay in phase space. The present simulations cannot distinguish these two decay modes. No obvious diproton emission was found.

Experimental study of the two-proton correlated emission from the excited states of Ne-17,Ne-18 and S-28,S-29

A series of experiments have been performed by complete kinematics measurements to study two-proton (2p) correlated emission from the excited states of Ne-17,Ne-18 and S-28,S-29 via the Coulomb excitation by bombarding on Au-197 target. 2p and residua coincident events were picked Out under strict conditions. Visible p-p correlations were observed. It is shown that 2p can be emitted from the high-lying excited states. 2p halo may lead to 2p emission with large spectroscopy factor for the states close to or beyond the threshold.

~(16)O + ~(28)Si全熔合激发函数研究及ΔE-E探测器系统的研制调试

ΔE-E望远镜探测器是用于重离子校反应测量的一种装置，它可以测量产物的电荷数和能量。在单路ΔE-E的基础上，我们研制了一路ΔE气体探测器和十路E金硅石垒探测器构成的多路ΔE-E望远镜探测系统。电离室窗直径为8cm，阴极到栅极距离为6cm，栅极到阳极距离为2cm，充入50的Ar(90%) + CH_4 (10%)气体，测得对~(241)Am的5.41Mev/α其能量分辩为13%。所用的十块金硅石垒探测器能量为1%左右。此系统可以同时测量22 °范围内的10个角度点，这对角分布测量将十分有利。该探测器系统对~(16)O + ~(12)C反应体的Z分辩约为6%，它可以清楚的分开C到Mg的各种元素。利用上述多路ΔE-E探测系统，我们测量了E_(16O) = 50Mev-90Mev的16_O束流轰击~RC、~(24)Mg、~(28)Si和~(32)S等四个体系校反应产物的角分布、能谱和激发函数。在测量激发函数时，我们选取能量步长为ΔE_(Lab) = 1Mev，以便观察振荡结构在角分布测量时，对于三个能量点，我们测量了5.1 °- 39 °范围内的13个角度点。由于时间限制，本毕业论文仅给出~(16)O + ~(28)Si反应的全熔合激发函数和角分布。并且运用G-M模型和Wiecki公式对全熔合截石进行了理论计算。从激发函曲线看，实验结果的平均趋势与G-M模型的理论结果符合的相当好，同时还发现了该体系全熔合截石随能量有规律的起伏，这种起伏具有公认的振荡结构和某些特征，因此这些起伏极有可能就是振荡结构

抢救“土壤水库”实为黄土高原生态环境综合治理与可持续发展的关键——四论黄土高原国土整治28字方略

现在全国上下深切关注着黄河的重大问题及其对策。其实问题的根源都出自人们对黄河流域尤其黄土高原自然资源的掠夺式开发 ,形成了“3个恶性循环”:广种薄收 ,薄收更广种 ,虽是罪魁祸首 ,但常反被忽视 ,致使生态环境脆弱 ,人民长期贫困 ;只有下游河床越淤越高 ,防洪大堤越筑越高 ,越高越险和断流历时越来越长 ,上溯速度越来越快 2个恶性循环的危害才使人惊恐。不难看出 ,这是恰与形成黄土高原自然规律完全相悖的人为地质过程的结果。可惜它还未引起人们深入充分的认识 ,难怪一向短缺一个为各家合力共识的治本对策。当今国家将经济发展的重点向中、西部转移 ,并要求重建一个山川秀美的大西北 ,黄土高原的持续开发与治理对策就显得更为举足轻重。由此其各项对策都将面临着转变观念、调整思路、实事求是地进行科学分析和抉择。笔者最近从陆地生态的发生发展及其整个地质历史演变过程的研究中发现 :“土壤水库”的发生发展及其演变是陆地生态发生发展的关键和“动力”,只要维护土壤水库的正常发展就能更好地保卫生态环境。黄土高原地区由于得天独厚的降尘堆积环境条件和持续的成壤过程 ,可使降水具有直接渗入“地下水库”的特殊功能。只要维护住高入渗土壤水库的存在就...

Synthesis, crystal structure, and thermal property of a novel supramolecular assembly: (NH42810424)(CHNO) O-[H(V)O(]2H)4(10)28(2), constructed from decavanadate and caffeine

A novel 3D supramolecular assembly constructed from decavanadate and caffeine building blocks, (NH4)(2)(C8H10N4O2)(4)[H4V10O28].2H(2)O (1), has been synthesized in aqueous solution and characterized by elemental analysis, IR, H-1 NMR, V-51 NMR, TG-DTA, and single crystal X-Ray diffraction. The compound 1 crystallizes in monoclinic system, space group P2(1)/n, a = 15.801(1) Angstrom, b = 12.914(1) Angstrom, c = 15.913(2) Angstrom, beta = 113.55degrees, V = 2976.4 (5) Angstrom(3), Z = 2, R = 0.0498 with 6818 reflections. Water molecules, ammonium ions, and caffeine act as "cement" linking the polyanions into 1D chain along the c-axis by hydrogen bonding. In compound 1, extensive hydrogen-bond contacts and strong pi-pi interactions lead to an ordered 3D supramolecular framework. TG-DTA curves indicate that the weight loss of the complex can be divided into three stages.

Kinetics of extraction and stripping of y(III) by Cyanex 272 as an acidic extractant using a constant interfacial cell with laminar flow

The extraction and stripping kinetics of yttrium(III) with bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272, HA) dissolved in heptane as an acid extractant have been investigated by constant interfacial cell with laminar flow. The experimental hydrodynamic conditions have been chosen so that the contribution of diffusion to the measured rate of reaction is minimized. The plot of interfacial area on the rate has shown a linear relationship, which makes the interface the most probable local for the chemical reactions. At the same time, the extraction thermodynamic and kinetic methods are compared to determine the equilibrium extraction constant. A rate equation and the rate-determining step of the extraction and stripping of yttrium(III) have also been obtained, respectively.

Kinetics of ytterbium(III) extraction with Cyanex 272 using a constant interfacial cell with laminar flow

Studies have been made on the kinetics of ytterbium(III) with bis-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272, HA) in n-heptane using a constant interfacial cell with laminar flow. The stiochiometry and the equilibrium constant of the extracted complex formation reaction between Yb3+ and Cyanex 272 are determined. The extraction rate is dependent of the stirring rate. This fact together with the Ea value suggests that the mass transfer process is a mixed chemical reaction-diffusion controlled at lower temperature, whereas it is entirely diffusion controlled at higher temperature. The rate equations for the ytterbium extraction with Cyanex 272 have been obtained. The rate-determining step is also made by predictions derived from interfacial reaction models, and through the approximate solutions of the flux equation, diffusion parameters and thickness of the diffusion film have been calculated.

Mass transfer kinetics of yttrium(III) using a constant interfacial cell with laminar flow. Part II. Extraction with Cyanex 272

The yttrium(III) extraction kinetics and mechanism with bis-(2,4,4-trimethyl-pentyl) phosphinic acid (Cyanex 272, HA) dissolved in heptane have been investigated by constant interfacial cell with laminar flow. The data has been analyzed in terms of pseudo-first order constants. Studies on the effects of stirring rate, temperature, acidity in aqueous phase, and extractant concentration on the extraction rate show that the extraction regime is dependent on the extraction conditions. The plot of interfacial area on the rate has shown a linear relationship. This fact together with the strong surface activity of Cyanex 272 at heptane-water interfaces has made the interface the most probable location for the chemical reactions. The forward, reverse rate equations and extraction rate constant for the yttrium extraction with Cyanex 272 have been obtained under the experimental conditions. The rate-determining step has been also predicted from interfacial reaction models. The predictions have been found to be in good agreement with the rate equations obtained from experimental data, confirming the basic assumption that the chemical reaction is located at the liquid-liquid interface.

Kinetics of Y(III) stripping for the system Y/HCl/Cyanex 272-P507/heptane with constant interfacial area cell with laminar flow

Kinetics and mechanism of stripping of yttrium(III) previously extracted by mixtures of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272, HA), and 2-ethylhexyl phosphonic acid mono-2-ethylhexl ester (P507, HB) dissolved in heptane have been investigated by constant interfacial-area cell by laminar flow. The corresponding equilibrium stripping equation and equilibrium constant were obtained. The studies of effects of the stirring rate and temperature on the stripping rate show that the stripping regime is dependent on the stripping conditions. The plot of interfacial area on the rate has shown a linear relationship. This fact together with the strong surface activity of mixtures of Cyanex 272 and P507 at heptane-water interfaces makes the interface the most probable locale for the chemical reactions. The stripping rate constant is obtained, and the value is compared with that of the system with Cyanex 272 and P507 alone. It is concluded that the stripping ability with the mixtures is easier than that of P507 due to lower the activation energy of the mixtures. The stripping rate equation has also been obtained, and the rate-determining steps are the two-step interfacial chemical reactions as predicted from interfacial reaction models.