多电子激发态离子的自由离衰变处理方法

在分析当前描述离子与原子碰撞的经典理论模型的基础上,详细讨论了处理多电子激发态自电离衰变问题的一些新的思路,把高电荷态离子与原子碰撞反应中的电子转移过程分为四阶段描述,并依据能量守恒原理,规范了处理多电子激发态离子发生自电离衰变的规则,自洽地解决碰撞中间过程中俘获多电子后的离子发生自电离向末态衰变的问题,并分析和比较了新的计算结果与实验结果。     

多电子激发态离子的自电离衰变处理方法

在分析当前描述离子与原子碰撞的经典理论模型的基础上,详细讨论了处理多电子激发态自电离衰变问题的一些新的思路,把高电荷态离子与原子碰撞反应中的电子转移过程分为四阶段描述,并依据能量守恒原理,规范了处理多电子激发态离子发生自电离衰变的规则,自洽地解决碰撞中间过程中俘获多电子后的离子发生自电离向末态衰变的问题,并分析和比较了新的计算结果与实验结果     

重离子束在热靶中的电子阻止本领与有效电荷数

采用线性介电响应理论,研究了重离子束在热靶中的有效电荷数和电子阻止本领。为了考虑入射离子的束缚电荷分布,我们将Brandt-Kitagawa的有效电荷理论推广到热靶。在低速和高速情况下,分别得到了有效电荷数和电子阻止本领的解析表示式。数值结果表明,对于低速离子,有效电荷数随电子气的温度增加而增加;在一定的温度范围内,低速离子的阻止本领与冷靶相比有明显增加。对于高速离子,我们的理论结果与实验值符合得较好。 关键词：     

10Neq+(q=1～3)的电荷损失截面

采用托马斯－费米近似和二体碰撞近似,计算了多电荷离子１０Ｎｅ＾ｑ＋与中性原子Ｈ和Ｈｅ碰撞的电荷损失截面以及电子的动量分布和离子势函数分布。     

低速高电荷态离子40Ar16+与云母表面作用中的电子发射研究

报道了由兰州ECR源提供的低速高电荷离子40Ar16 入射到云母表面产生的电子发射的实验测量结果.结果发现,电子发射产额Y与离子入射角ψ有近似1/tanψ的关系.基于经典过垒模型,我们对这一关系进行了理论分析.实验结果和理论结果相当符合,这就间接说明势能电子发射是低速高电荷态离子作用于表面发射电子的一个主要途径.     

高电荷态Ar^q＋与Ne碰撞中入射离子电荷交换截面的研究

报道Ar^q 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Ar^q 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。     

强激光与高密度气体相互作用中电子和离子加速的数值模拟

在现有的一维粒子模拟程序的基础上发展了带光电离和碰撞电离及蒙特卡罗两体碰撞的模拟程序(1D PIC-MCC). 用此程序模拟研究了短脉冲激光与He气靶相互作用时电子和离子的加速过程. 研究表明当强激光与过临界密度的微米厚度的平面靶相互作用时，靶前表面物质将被激光脉冲前沿迅速离化；新生的电子被激光场有质动力加速成为高能电子，这些电子穿入到靶内，通过电子碰撞电离离化靶内物质；一部分高能电子穿透靶后，会在靶的后表面形成强的电荷分离场，该场迅速离化靶后表面物质，同时使得后表面离子得到加速. 部分穿透靶的超热电子将被电荷分离场重新拉回靶内，在靶的前后表面振荡. 一些振荡电子在此过程中得到电荷分离场加速，离开前表面，在前表面也形成电荷分离场，使前表面离子得到加速. 关键词： 激光等离子体 光电离和碰撞电离 电子加速 离子加速     

高电荷态离子207Pbq+(24≤q≤36)与Si(110)固体表面作用的电子发射研究

报道了利用兰州重离子加速器国家实验室ECR源引出的高电荷态离子²⁰⁷Pb^q+(24≤q≤36)入射到Si(110)表面产生的电子发射的实验测量结果.结果表明,高电荷态离子与固体表面相互作用产生的电子发射产额Y与入射离子的电荷态q、入射角度ψ和入射能量E都有很强的关联.首次发现,电子发射产额Y与入射角度ψ间有接近1/tanψ的关系.理论分析认为,这些过程与基于经典过垒模型的势能电子发射过程密切相关. 关键词： 高电荷态离子 经典过垒模型 电子发射产额     

高电荷态离子207Pbq+(24≤q≤36)与Si(110)固体表面作用的电子发射研究

报道了利用兰州重离子加速器国家实验室ECR源引出的高电荷态离子207Pbq+(24≤q≤36)入射到Si(110)表面产生的电子发射的实验测量结果.结果表明,高电荷态离子与固体表面相互作用产生的电子发射产额Y与入射离子的电荷态q、入射角度ψ和入射能量E都有很强的关联.首次发现,电子发射产额Y与入射角度ψ间有接近1/tanψ的关系.理论分析认为,这些过程与基于经典过垒模型的势能电子发射过程密切相关.     

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.     

Spatial and angular distribution of the heavy ion charge under channeling in crystals

A kinetic theory of passage of multiply charged heavy ions through crystals is developed that allows for diffusion in the transverse momentum space and ion-crystal charge exchange. The theory provides an adequate explanation for the observed angular distributions of heavy ions passing through oriented crystals, makes it possible to calculate the partial angular distributions of different charge states, and treats the discovered effects of “cooling” and “heating” of channeled ion beams in physical terms. The angular and spatial distribution of channeled ions with different energies is calculated. Whether a channeled beam of multiply charged heavy ions will be cooled or heated is related to the dependence of the electron capture and loss probabilities on the impact parameter when the ions interact with atomic chains. This interaction governs the run of the angular and spatial distribution of the channeled ion charge.     

Observation of persistent flow of a Bose-Einstein condensate in a toroidal trap

We have observed the persistent flow of Bose-condensed atoms in a toroidal trap. The flow persists without decay for up to 10 s, limited only by experimental factors such as drift and trap lifetime. The quantized rotation was initiated by transferring one unit variant Planck's over 2pi of the orbital angular momentum from Laguerre-Gaussian photons to each atom. Stable flow was only possible when the trap was multiply connected, and was observed with a Bose-Einstein condensate fraction as small as 20%. We also created flow with two units of angular momentum and observed its splitting into two singly charged vortices when the trap geometry was changed from multiply to simply connected.     

MIS-1 electron-beam ion source

The Institute of Nuclear Physics (INP) has developed and produced electron-beam multiply charged ion sources. These ion sources give the electron beam its high density in the ionization area, at the ion trap ≥10³ A/cm². They produce multiply charged ions of various elements, both gaseous and solid ones. These ion sources successfully employ the technique of the dozed inlet of solid-element atoms into the ion trap.     

Anomalous heat flux inhibition under high frequency radiation pulse absorption in electron-ion collisions

Anomalous heat flux inhibition under high frequency radiation pulse absorption in electron-ion collisions is revealed for plasma with multiply charged ions. The inhibition takes place in time moments greater than momentum relaxation time, but less than energy relaxation time of the electrons, which give main contribution to the heat flux value.     

Spectroscopy using stimulated electron–ion recombination

Spectroscopic results obtained on multiply charged few electron ions by using laser stimulated two-step recombination in ion storage rings are presented in an overview. Line splittings in transitions between Rydberg levels were observed for helium like and beryllium like ions. Emphasis is given to results on the beryllium like system N³⁺ where information about the splitting between high angular momentum levels (l⩾4) was obtained for the Rydberg levels n=13 and 8 with experimental errors of about ±0.02 meV. This revised version was published online in August 2006 with corrections to the Cover Date.     

Charge composition of metal ions versus laser radiation density in laser mass spectrometry

From experimental data for the yield of differently ionized ions at laser mass spectrometry, the dependence of the charge composition of the ions on the laser radiation density is found for a number of metals. It is established that the amount of multiply charged ions predominates over low-charged ones when the radiation density grows. An explanation is given for the fact that singly charged ions prevail over multiply charged ones at the end of laser-induced plasma spread. The influence of recombination on the ion distribution in the mass spectrum is estimated.     

Secondary ion emission under the bombardment of Si by multiply charged Si q+ ions

The spectra of secondary ion emission under the bombardment of a B-doped Si target by multiply charged Si ^q+ ions (q = 1?C5) have been studied in the energy range of 1 to 10 keV per unit of charge. A multifold increase in the yield of secondary cluster Sk _n ⁺ ions, multiply charged Si ^q/+ ion (q = 1?C3), and H⁺, C⁺, B⁺, Si₂N⁺, Si₂O⁺ is observed as the charge of the multiply charged ions increases. The increase in the yield of secondary ions with increasing charge of the multiply charged-ion charge is most significant for ions with relatively high ionization potentials.     

纳秒激光电离分子团簇产生高价离子实验研究

 利用飞行时间质谱仪，研究了功率密度为10⁹~10¹¹ W/cm²，波长为532 nm 的纳秒激光对苯、呋喃、甲醇及碘甲烷分子团簇的激光电离过程。实验观察到了高平动能的高价离子C^q+(q≤3)，O^q+(q≤3)和I^q+(q≤4)，该过程经历了以“初始的多光子电离引发-逆轫致吸收加热-电子碰撞电离模式”为主的激光团簇作用过程，后期经历了团簇的库仑爆炸过程。实验发现：即使激光能量变化一个量级以上时，主要高价离子的种类及占全部离子产物的比率也没有明显的变化，但是高价离子的初始平动能随激光强度的增大而增加；分子中含有较多个外壳层电子的氧、碘原子更容易电离产生高价离子，而碳离子的价态和强度相对较低。     

纳秒激光电离分子团簇产生高离化离子的激光波长效应

 利用脉冲分子束-激光电离-飞行时间质谱仪，在10⁹～10¹² W·cm^-2激光功率密度条件下，考察了Nd：YAG激光器输出的1 064，532，266 nm波长的激光与苯、氨、硫化氢等团簇的相互作用。发现1 064 nm的激光可以电离分子束产生高离化态的C⁴⁺，N⁵⁺，S⁶⁺等离子；波长为532 nm的激光则电离产生价态较低的C³⁺，C²⁺，N³⁺，N²⁺， S⁴⁺，S³⁺以及S²⁺ 等离子；在266 nm波长条件下进行实验，没有产生任何高价离子。提出了一个“多光子电离引发-逆轫致吸收加热-电子碰撞电离”模型来解释高价离子的产生。激光场下电子在团簇内部的逆轫致加热是整个过程的关键步骤，电子被加热的速度正比于激光波长的平方。这可以解释为何长波长的激光有利于更高价态离子的产生。     

Inelastic processes in the collision of fast multiply charged ions with a hydrogen molecule

The collision of a fast (including relativistic) multiply charged ion with the simplest (hydrogen) molecule is considered on the basis of the eikonal approximation. The analytical formula for the reaction cross section, i.e., the total cross section of all inelastic electron processes in the domain where the Born approximation is inapplicable, is derived. The cross section is compared to the corresponding doubled inelastic cross sections for collisions of multiply charged ions with hydrogen atoms calculated within perturbative and nonperturbative approaches.