C3+与Ne碰撞过程纯电离绝对截面的测量和研究

介绍了离子-原子碰撞过程中双微分绝对截面的计算方法.利用符合技术测量了中能区C³⁺+Ne碰撞系统的纯电离微分绝对截面. 将实验结果与多体经典蒙特卡罗方法计算结果进行对比后发现，纯电离截面随入射能量变化的趋势基本一致，对理论与实验产生差异的原因作了分析. 对多重电离的电离机制分析表明：高价态的反冲离子主要来自于俄歇贡献；随着入射能量的升高，电子-电子间的库仑作用也逐渐显现. 此实验方法可以用于相同实验装置上的各种反应出射道的绝对截面测量，入射离子种类及入射离子能量范围将得到拓展. 关键词： 离子-原子碰撞 绝对截面 纯电离     

碳离子碰撞引起的金L壳层X射线产生截面的实验研究

实验测量了20～50 MeV的C离子和Au原子碰撞中Au产生的L壳层X射线,研究了Au的L各支壳层产生截面σ(L_l)、(L_α)、(L_β)、(L_γ)和总截面的比值σ(L_(total)与入射离子能量的关系.利用L壳层的辐射跃迁几率,Croster～Kroning跃迁率和L亚壳层的荧光产额将平面波波恩近似(PWBA)和ECSSR理论计算的电离截面转换为L层X射线产生截面,并与实验结果相比较,结果表明σ(L_l)、(L_α)、(L_γ)和总截面σ(L_(total))实验测量值随入射离子的变化趋与ECPSSR和PWBA所预测的结果一致,ECSSR理论值更接近我们的实测测量值,但是数值大于实验测量结果.     

C3+与Ne碰撞过程纯电离绝对截面的测量和研究

介绍了离子-原子碰撞过程中双微分绝对截面的计算方法.利用符合技术测量了中能区C3++Ne碰撞系统的纯电离微分绝对截面.将实验结果与多体经典蒙特卡罗方法计算结果进行对比后发现,纯电离截面随入射能量变化的趋势基本一致,对理论与实验产生差异的原因作了分析.对多重电离的电离机制分析表明:高价态的反冲离子主要来自于俄歇贡献;随着入射能量的升高,电子-电子间的库仑作用也逐渐显现.此实验方法可以用于相同实验装置上的各种反应出射道的绝对截面测量,入射离子种类及入射离子能量范围将得到拓展.     

高电荷态Arq+与Ne碰撞中入射离子电荷交换截面的研究

报道Arq++Ne(q=8, 9, 11, 12)碰撞体系中多电子转移过程,得到了多组实验测量电荷交换截面数据,讨论入射离子电荷交换截面、反冲离子产生截面与入射离子电荷态、能量以及散射离子电荷态的关系,并且将实验结果与Arq++Ar碰撞体系进行对比研究.在修正分子库仑过垒模型的基础上,对实验现象做了合理的解释.     

低能He2+-He反应中单电子俘获微分散射过程的实验研究

利用冷靶反冲离子动量谱仪装置系统研究了20—40 keV He²⁺-He碰撞体系的态选择单电子俘获过程,实验获得了单电子俘获过程的态选择截面以及角微分截面.在所研究的能区范围,电子俘获到L壳层的截面最大,为主要的反应道,这与分子库仑过垒模型的反应窗理论的预测一致.实验测量的态选择截面与原子轨道紧耦合的计算结果很好地符合,与光谱方法的测量结果存在一定的差别,主要原因是光谱方法不能测量完整的反应通道信息.实验结果表明,总角微分截面在小角度范围主要来源于电子俘获到基态的贡献,在大角度范围主要来自电子俘获到激发态的贡献;电子俘获到基态的和激发态的角微分截面均出现振荡结构,这种振荡来源于电子俘获反应中分子轨道之间的相干效应.实验测量的角微分截面与其他实验和紧耦合方法的计算结果进行了比较和分析. 关键词： 冷靶反冲离子动量谱仪 态选择电子俘获 态选择截面 角微分截面     

原子轨道方法研究He2+-He碰撞中电荷转移过程

应用双中心的原子轨道强耦合方法研究了He2+-He碰撞中的电荷转移过程,计算了随入射离子能量变化的单电子俘获总截面及各个次壳层的态选择截面,并与其它理论结果和实验结果进行了比较,发现我们的理论结果与实验很好的符合.针对中国科学院近代物理研究所最近的实验测量,我们也计算了电荷转移过程的微分截面.     

等电荷态离子与He原子碰撞中的转移电离过程研究

采用位置灵敏探测和飞行时间技术测量了等电荷态离子Cq+、Nq+、Oq+、Neq+(q=4,5,6,7)与He原子碰撞中,转移电离截面与单电子俘获截面的比值R.研究了相同q入射的情况下,R与入射离子核电荷数Z的依赖关系,在统计蒸发模型的基础上对实验结果进行了解释.     

氦原子与氯离子碰撞过程中电子损失的研究

反冲离子飞行时间-散射离子位置灵敏符合技术及多参数获取系统测量了2 MeV～8 MeV的氯离子撞击氦原子,伴随氯离子电子损失过程氦的双、单重电离相对截面比;及氦原子被电离伴随的氯离子的双、单电子损失相对截面比.对测量结果进行了分析讨论.     

Cq+(q=1-4)与He,Ne,Ar碰撞的电子损失截面测量与研究

在中能区测量了C^q+(q=1-4)与He,Ne,Ar气体原子碰撞的电子损失截面,计算分析了入射离子损失两个电子与一个电子的总截面比 R₂₁. 单反应道分析无法完全解释所有实验结果,必须同时考虑入射离子的电子损失、电子俘获和靶原子电离各种出射道间的耦合作用. 对于不同靶原子的碰撞,入射离子损失一个电子和两个电子的速度阈值可以由屏蔽和反屏蔽理论解释. 然而,该理论不能完全解释截面比 R₂₁ 关键词： 离子-原子碰撞 截面 电子损失     

低能高电荷态氩离子与氩原子碰撞反应截面研究

使用位置灵敏技术和飞行时间方法研究了低能高电荷态氩离子与氩原子的碰撞反应,给出了实验测量得到的入射离子电荷交换截面和转移电荷截面,研究了反应截面与不同电荷态参教的关系,并与修正后的分子过垒模型计算结果进行了比较。     

Model of β-CO on Mo(100): Dissociative adsorption

Secondary ion production during ion bombardment is analyzed experimentally. Secondary ions consist of bulk ions and surface ions. The former originates in the bulk material and the latter in the adsorbed layer. The most probable kinetic energy of bulk ions is higher by several tens of eV than that of surface ions, In order to perform quantitative bulk analysis the surface ions should be removed from the mass spectrum by making use of the difference between these kinetic energies. Secondary ion measurements indicate that the recoil implantation of an adsorbed element occurs to a significant extent under low ion current density bombardment.     

Shift of the proton NMR field in aqueous solutions of paramagnetic ions

In the paper there is discussed the proton NMR field shift in aqueous solutions of transition metal ions, which has to be taken into account in exact measurements of the static magnetic field. Using the results of Luz's and Shulman's measurements (1965) the empirical expression for the field shift is evaluated, which is a function of the sample shape, of the concentration and the susceptibility of paramagnetic ions in the solution. It is shown that in exact field measurements the diamagnetic part of the susceptibility of the solution cannot be neglected and that one may eliminate the field shift by a suitable choice of the paramagnetic-ions concentration in transversely magnetized cylindrical samples.     

Effect of Co substitution on magnetic properties of Sr14Cu24O41

A series samples of Sr₁₄(Cu_1−xCo_x)₂₄O₄₁ (x=0, 0.02, 0.06, 0.14, 0.18) were prepared by standard solid-state reaction. X-ray diffraction measurements show that all the samples are single phase and their lattice parameter hardly changes by Co dopant. Electron diffraction experiments and X-ray photo-emission spectroscopy measurements reveal that Co ions substituted Cu ions in the chain. The measurements of magnetic susceptibility from 10 to 300 K in an applied magnetic field of 1.0 T show that Co dopant induces increase in susceptibility. The spin gaps are observed in all the samples, and decrease with increase in Co doping concentration. Fitting of the date indicates that strong antiferromagnetic interaction is induced and antiferromagnetic dimeried state may be formed due to Co³⁺ ions doping in these compounds.     

稀土原子与离子的自然辐射寿命测量

概述了当前自由原子和离子的激发态自然辐射寿命测量技术的进展。以LaⅠ和PrⅡ为例,系统介绍了几种稀土元素自由原子和离子激发态寿命测量技术并分析了它们的优缺点;以SmⅡ为例,详细介绍了激光烧蚀产生自由原子(离子)技术及结合激光诱导荧光时间分辨光谱技术进行激发态寿命测量的优缺点。最后,探讨了改进上述技术局限性的解决思路,以期进一步提高辐射寿命测量的精确度。     

Determination of electron temperature in low pressure gas discharges by resonant laser light scattering

It is shown that the electron temperature in low pressure discharges can be estimated from the drift velocity of the ions towards the wall. Velocity measurements by resonant laser light scattering lead to electron temperatures consistent with such values obtained by probe measurements.     

Ionic conductivity and anion diffusion in single crystals of lead chloride

The ionic conductivity and self-diffusion of chlorine ions in undoped single crystals of zone-refined lead chloride have been measured over the temperature range 625–370K. These measurements suggest that the conductivity and self-diffusion are due to simple vacancy migration as confirmed by the observed correlation factor. The activation energy of formation of vacancies is found to be 1.55 eV and that for migration of an anion is 0.38 eV. In the extrinsic region, the two measurements show marked discrepancies which are explained by assuming the presence of oxygen impurity ions in the lattice, and the mechanisms for their contribution to the observed excess conductivity are discussed.     

Influence of atomic to molecular conversion on the diffusion of ions

An analytical relation which describes the diffusion of positive ions is derived taking into account the process of conversion of atomic ions into molecular ions. The theoretically obtained results can be used for the interpretation of free diffusion measurements, and also for the derivation of the reaction rate coefficient from these measurements.     

哺乳动物尿液中钙镁离子浓度的1H NMR测定方法

哺乳动物体液中的钙镁离子浓度能够反映体内营养代谢的平衡与一些疾病的发生发展. 尿液中钙镁离子浓度的准确测量需要不受基质影响的便捷新方法. 该文使用过量乙二胺四乙酸(EDTA)为探针并通过¹H NMR方法测定钙镁离子与EDTA络合物的含量,建立了一种快速原位的尿液钙镁离子浓度测量方法. 将此方法分别用于人、大鼠及小鼠的尿液测定,发现3类哺乳动物的尿液钙镁离子浓度存在显著的物种依赖性和较大的相同物种个体间差异. 上述为生物体液中钙镁离子浓度的快速定量测量提供了便捷方法,也提供了3类哺乳动物尿液钙镁离子浓度的基础数据.     

Electrical and structural properties of diamond films implanted by various doses of oxygen ions

Oxygen-doped diamond films are prepared by implanting various dose oxygen ions into the diamond films synthesized by hot filament chemical vapour deposition, and their electrical and structural properties are investigated. Hall effect measurements show that lower dose oxygen ion implantation is beneficial to preparing n-type diamonds. The carrier concentration increases with the dose increasing, indicating that oxygen ions supply electrons to the diamonds. The results of AES spectrum indicate that oxygen ions are doped into the diamond films, and the O-implanted depth is around 0.1μm. Raman spectrum measurements indicate that the lower dose oxygen ion implantation at 10¹⁴cm^-2 or 10¹⁵cm^-2 is favourable for producing less damaged O-doped diamond films.