基于多体经典轨迹蒙特卡罗方法的H+,Li3+,Be4+,O7+与He原子电荷交换过程

经典轨迹蒙特卡罗(CTMC)方法是研究离子-原子碰撞系统电荷交换过程的常用方法,广泛应用于天体物理以及实验室等离子体环境下重粒子碰撞过程的研究.本文利用四体碰撞模型(4-CTMC)研究了包括两个束缚电子的四体碰撞过程,通过数值求解四体碰撞系统的哈密顿运动方程,计算了高电荷态入射离子(Li³⁺,Be⁴⁺和O⁷⁺)同氦原子在大能量范围的单、双电子电离和俘获截面.H⁺+He碰撞截面的计算中,在50—200 keV/amu的入射能区,4-CTMC的结果几乎重复了实验结果.在高电荷态入射情形下,4-CTMC计算的单电子电离和俘获截面值相较于三体碰撞模型(3-CTMC)在100—500 keV/amu的入射能区内与实验符合更好.尽管4-CTMC和3-CTMC忽略了电子关联,均高估了双电子电离和俘获截面(与实验值相比),但4-CTMC的结果更接近实验.     

双电荷离子He2+与Ne,Ar原子碰撞中的激发态

实验用光学多道分析系统(OMA)测量了He²⁺和Ne,Ar碰撞过程中的发射光谱,结果表明,这些碰撞体系存在着三种激发过程:双电子俘获激发过程、单电子俘获激发过程和直接激发过程。给出了HeI,HeII,NeI,NeII和ArI,ArII谱线的发射截面,并对He²⁺+Ne和He²⁺+Ar两个碰撞体系的发射截面作了一些比较,发现在入射离子速度相同的情况下,后者的发射截面要比前者大得多,并对此进行了定性讨论。OMA的光谱波长范围为200—800nm。入射离子He²⁺的能量范围为140—340keV。 关键词：     

He+和He2+离子与碱金属原子Na碰撞中靶激发过程的实验研究

本文通过光学方法,在q×(20—140)keV能量范围内,研究了He⁺和He²⁺离子与碱金属原子Na碰撞中的靶激发过程。通过光学多道分析系统(OMA),对He⁺与Na碰撞过程,观察到NaI589.0+589.6nm(3p→3s),NaI818.3nm(3d→3p)和NaI568.8nm(4d→3p)等谱线。对He²⁺与Na碰撞过程,只观察到NaI589.0+589.6nm谱线。计算了所有观察到的谱线的发射截面和Na(3 关键词：     

高电荷态离子N6+与He原子碰撞激发过程的实验研究

利用电子迴旋共振(ECR)多电荷离子源产生的高电荷态离子束和LHT-30VUV真空紫外单色仪,对N⁶⁺与He碰撞激发过程进行研究,观察到三种碰撞激发过程:(1)单电子俘获;(2)双电子俘获;(3)入射离子直接激发过程。 关键词：     

He+和He2+离子与碱金属原子Li碰撞中的靶激发

本文在q×(20—150)keV的能量范围内,通过光学测量,对He⁺和He²⁺离子与碱余属原子Li碰撞过程中的靶激发过程进行了研究。由光学多道分析系统(OMA),测得LiI 670.8nm(2p→2s),LiI610.4nm(3d→2p),LiI460.3nm(4d→2p)和LiI812.6nm(3s→2p)谱线。给出所观察到的谱线的发射截面和相立的Li(2p)激发截面。对He⁺与Li碰撞过程,LiI670.8nm谱线发射截面与Aumayr 关键词：     

Ar16+和Ar17+离子与Zr作用产生的X射线谱

将超导离子源提供的10—20keV/q Ar¹⁶⁺和Ar¹⁷⁺离子入射到Zr金属表面,在相互作用中产生的X射线谱表明,高电荷态Ar¹⁶⁺离子在金属表面中性化过程中有可能存在多电子激发,使Ar¹⁶⁺的K壳层电子被激发形成空穴,在退激过程中发射特征Kα-X射线.空心原子Ar的K层发射X射线强度随入射离子的动能而减弱,靶原子Zr的L壳层发射X射线强度随入射离子动能的增加而增强.Ar¹⁷⁺的单离子的Kα- 关键词： 高电荷态离子 空心原子 X射线     

纳秒强激光中丙酮团簇增强的多价电离现象

利用脉宽为25 ns的脉冲Nd: YAG 532 nm的激光，在10¹⁰—10¹¹ W/cm²的强度下，用飞行时间质谱对丙酮团簇的激光电离过程进行了研究. 观察到了较强的O^q+(q=2—4)和C^q+(q=1—4)高价离子信号，这些高价离子 C⁴⁺，C³⁺，C²⁺，O⁴⁺，O³⁺，O²⁺的最大概然平动能分别为240 eV，70 eV，30 eV，90 eV，80 eV，40 eV. 高价离子的强度和平动能随激光强度的增大而增大. 我们提出一个多光子电离引发，逆韧致吸收加热-电子碰撞电离模型来解释高价离子的产生. 关键词： 丙酮 团簇 库仑爆炸 高价离子     

He+离子和Ne原子碰撞过程中激发态的研究

在He⁺离子和Ne原子碰撞过程中,我们发现两种碰撞激发过程,一种是电子俘获激发过程,另一种是直接激发过程。本实验用光学多道分析系统(OMA)对这些过程进行了光学测量,给出了发射截面数据。入射离子实验室能量范围为70—150keV。 关键词：     

中低能非全裸C离子与He原子的碰撞研究

采用反冲离子飞行时间-散射离子位置灵敏符合测量技术，测量了能量范围在0.7v₀—4.4v₀(v₀为玻尔速度)的碳离子C^q+(q=1—4)与He原子碰撞过程不同出射道靶原子的双电离与单电离截面比R，包括入射离子不损失电子(直接电离)的出射道(R_q,q),入射离子俘获一个电子的出射道(R_q,q-1)和入射离子损失一个电子的出射道(R_q,q+1)，并研究了R随入射C离子的能量及电荷态的变化关系.实验表明，对给定电荷态的入射离子，靶原子的双电离与单电离截面比R与出射道有很强的依赖关系，即R_q,q<R_q,q+1<R_q,q-1.直接电离出射道截面比R_q,q与入射离子电荷态几乎无关，而入射离子俘获一个电子的出射道和损失一个电子的出射道靶原子双电离与单电离截面比R_q,q-1和R_q,q+1却与入射离子电荷态有很强的关系.采用原子极化理论和电子屏蔽与反屏蔽作用对实验结果进行了解释. 关键词： 离子-原子碰撞 电离 截面比     

强扰动能区非全裸C$lt;sup$gt;$lt;i$gt;q$lt;/i$gt;+$lt;/sup$gt;，O$lt;sup$gt;$lt;i$gt;q$lt;/i$gt;+$lt;/sup$gt;($lt;i$gt;q$lt;/i$gt;=1—4)与He原子碰撞过程中截面比的实验研究

利用兰州大学2×1.7 MV串列加速器离子-原子碰撞实验终端上产生的单核子能量为20—500 keV的C^q+和O^q+（q=1—4）离子与He原子碰撞.采用符合测量方法和多参数数据获取系统得到了散射离子与反冲离子电荷态的二维谱,从而分别得到直接电离、入射离子俘获电子和入射离子损失电子截面与总截面的截面比R^direct, R^capture和R^loss,并对强扰动能区的各个反应道之间竞争关系及同一反应道在不同碰撞体系中所表现出的实验规律进行了比较和定性分析. 关键词： 离子-原子碰撞 截面比 竞争关系 强扰动区     

Ionisation and fragmentation of tetraphenyl iron (III) porphyrin chloride induced by slow multiply charged ion impact

Ionisation and ion-induced fragmentation of tetraphenyl iron (III) porphyrin chloride (FeTPPCl) molecules have been studied after slow collisions (v∼ 0.2 a.u.) with multiply charged ions (O³⁺, Ar⁸⁺). Intact molecules and large fragments are observed in charge states up to q=4. For q=1, the intact molecule is the most abundant species, in particular, when projectiles in higher charge states are used. When the internal energy of the singly charged ion is increased by the energy transfer during the collision, the singly charged system de-excites by the emission of a neutral Cl-atom, a free electron or possibly a negative Cl anion. The processes are observed as direct as well as delayed processes on a μs-time scale. For q=2 to 4 the loss of the Cl-atom and some phenyl groups becomes more likely due to the lower stability and the larger energy transfer. The charge state distribution of atomic fragments is found to be very different, in particular, when C^q+ and Cl^q+ ions are compared. In the first case mainly singly charged ions are detected, whereas in the second case ions in charge states up to q=6 are observed with high intensities. These phenomena are discussed in terms of the intramolecular charge mobility.     

Elementary processes during collisions of ions with tryptophan molecules

The relative cross sections of elementary processes occurring in single collisions of tryptophan molecules in the gaseous phase with He²⁺ ions with energy 4 keV/u are measured using time-of-flight mass spectrometry for studying the mechanism of radiation damage of amino acid molecules. The fragmentation channels for intermediate singly and doubly charged tryptophan molecular ions formed during one-electron capture, two-electron capture, and electron capture with ionization are investigated. Significant difference is observed in the mass spectra of fragmentation of intermediate doubly charged ions formed during the capture with ionization and double capture, which is associated with different energies of excitation of {C₁₁H₁₂N₂O₂}²⁺* ions.     

K-shell ionization cross section of aluminium induced by low-energy highly charged argon ions

Al K-shell X-ray yields are measured with highly charged Ar^q+ ions (q=12–16) bombarding against aluminium. The energy range of the Ar ions is from 180 to 380 keV. K-shell ionization cross sections of aluminium are also obtained from the yields data. The experimental data is explained within the framework of 2pπ -2pσ rotational coupling. When Ar ions with 2p-shell vacancies are incident on aluminium, the vacancies begin to reduce. Meanwhile, collisions against Al atoms lead to the production of new 2p-shell vacancies of Ar ions. These Ar 2p-shell vacancies will transfer to the 1s orbit of an Al atom via 2pπ-2pσ rotational coupling leading to the emission of a K-shell X-ray of aluminiun. A model is constructed based on the base of the above physical scenario. The calculation results of the model are in agreement with the experimental results.     

Multiple ionization of argon accompanied by electron loss and capture of 0.22-6.35 MeV C^q＋ ions

In this paper a projectile ions recoil ions coincidence technique is employed to investigate the target ionization and projectile charge state changing processes in the collision of 0.22-6.35 MeV Cq^＋ （q = 1 - 4） ions with argon atoms. The partial cross section ratios of the double, triple, quadruplicate ionization to the single ionization （or the single capture） of argon associated with single electron loss （or single electron capture） by the projectile are measured and compared with the previous experimental results. In the present experiment, it is observed that the ratios of ionization cross sections R associated with single loss and single capture depend strongly on the projectile charge state and vary significantly with different reaction channels as impact energy increases. In addition, this paper gets empirical scaling laws for the ionization cross section ratios R corresponding to the projectile single loss and finds that the ratios of the double ionization to the single ionization associated with single electron capture remain constant in the present energy range.     

Effect of the target density on the cross section of charge exchange between fast ions and atoms

When fast X^q+ X^{q^ + } ions collide with atomic or molecular targets, the total charge exchange cross section decreases with increasing target density. This is because the excitation levels of resulting X^{(q - 1)+} X^{(q - 1)^ + } ions are suppressed because of ionization by target atoms. The effect of target density on the total charge exchange cross section may amount to one order of magnitude or more depending on the charge and energy of an incident ion, as well as on the density and inner shell configuration of target atoms. Numerical calculations are performed for partial (in the principal quantum number n) cross sections σ(n) and total cross sections σ_tot=Σ_nσ(n) of charge exchange in the case of collisions of fast multiply charged ions having an energy E in the range 100 keV/u-10 MeV/u with gas or solid targets.     

Secondary ion and Auger electron emissions from Ar+-ion-sputtered FeAl alloys

Some FeAl alloys, and pure Al and Fe samples, are sputtered in ultrahigh vacuum with Ar⁺ ions between 4 and 15 keV. As previously observed with CuAl alloys, the intensity of the principal Al Auger peak at 63.5 eV is a parabolic function of the Al concentration. Symmetric collisions Al → Al are thus much more efficient for Auger emission from pure aluminium than asymmetric collisions Ar → Al, the proportion of which among effective collisions hardly reaches 20% at 15 keV. Whatever the initial ion energy, the intensities of singly charged atomic secondary ions Al⁺ and Fe⁺, normalized to pure metals, are equal to the atomic concentration of the corresponding elements, whereas the normalized intensities of the multiply charged ions Al²⁺ and Al³⁺ are roughly equal to the square of Al concentration. These results agree with the occurence of two mechanisms in intrinsic ion emission: an electronic excitation process during the separation of the outgoing particle from the target (singly charged ions) and a collisional process from the symmetric collisions Al → Al only, with multiple Auger de-excitation outside the target (multicharged ions of light elements).     

Neutralization process of Xe^q＋ ion grazing on Al（111） surface

A code has been developed to simulate the neutralization and grazing process of slow highly charged ion Xe^q＋ on Al（111） surface under the classical-over-the-barrier model. The image energy gain of Xeq＋ ions are calculated and compared with experiment data. The simulation results of image energy gain are in good agreement with the experiment data. Meanwhile, in the present work, the reflection coefficient of incident Xe^q＋ on Al（111） surface as a function of the incidence angle, energy and charge state is also studied.     

Experimental study of single- and double-electron-capture by Ne ions from He gas

In the present work, the total cross-sections for single- and double-electron-capture by low-energy highly-charged Ne^q+ (q =2-6) recoil ions from He atomic gas have been measured in the energy range 600–1000 eV/q. These measurements are compared with other available experimental results. The charge state dependence of the single-electron-capture cross-sections for Ne^q+ (q = 2-6) recoil ions incident on He at energy of 1000 eV/q is compared with the theoretical predictions of the absorbing sphere model and the classical model.