Single-electron capture in keV Ar15+...18++He collisions

Single-electron capture in 14 keV q(-1) Ar15+...18++He collisions is investigated both experimentally and theoretically. Partial cross sections and projectile scattering angle dependencies have been deduced from the target ion recoil momenta measured by the COLTRIMS technique. The comparison with close-coupling results obtained from a two-centre extension of the basis generator method yields good overall agreement, demonstrating the applicability of close-coupling calculations to collision systems involving highly charged ions in charge states up to 18+.

高电荷态离子与Si(110)晶面碰撞的沟道效应研究

不同电荷态低速离子(Arq+，Pbq+)轰击Si(110)晶面，测量不同入射角情况下的次级粒子的产额. 通过比较溅射产额与入射角的关系，证实沟道效应的存在. 高电荷态离子与Si相互作用产生的沟道效应说明溅射产额主要是由动能碰撞引起的. 在小角入射条件下，高电荷态离子能够增大溅射产额. 当高电荷态离子以40°—50°入射时，存在势能越高溅射产额越大的势能效应.

X-ray spectra induced by Xe-129(q+) impacting the metal surface

Using the slow highly charged ions Xe-129(q+) (q = 25, 26, 27; initial kinetic T-0 <= 4.65 keV/a.u.) to impact Au surface, the Au atomic M alpha characteristic X-ray spectrum is induced. The result shows that as long as the charge state of projectile is high enough, the heavy atomic characteristic X-ray can be effectively excited even though the incident beam is very weak (nA magnitude), and the X-ray yield per ion is in the order of 10(-8) and increases with the kinetic energy and potential energy of projectile. By measuring the Au M alpha-X-ray spectra, Au atomic N-level lifetime is estimated at about 1.33x10(-18) s based on Heisenberg uncertainty relation.

Multi-electron processes in 4.15-11.08 keV/u(13)C(6+) on argon collisions

The relative partial cross sections for C-13(6+)-Ar collisions at 4.15-11.08 keV/u incident energy are measured. The cross-section ratios sigma(2E)/sigma(SC), sigma(3E)/sigma(SC), sigma(4E)/sigma(SC) and sigma(5E)/sigma(SC) are approximately the constants of 0.51 +/- 0.05, 0.20 +/- 0.03, 0.06 +/- 0.03 and 0.02 +/- 0.01 in this region. The significance of the multi-electron process in highly charged ions (HCIs) with argon collisions is demonstrated (sigma(ME)/sigma(SC) as high as 0.79 +/- 0.06). In multi-electron processes, it is shown that transfer ionization is dominant while pure electron capture is weak and negligible. For all reaction channels, the cross-sections are independent of the incident energy in the present energy region, which is in agreement with the static characteristic of classic models, i.e. the molecular Coulomb over-the-barrier model (MCBM), the extended classical over-the-barrier (ECBM) and the semiempirical scaling laws (SL). The result is compared with these classical models and with our previous work of C-13(6+)-Ne collisions

ATOMIC PHYSICS RESEARCHES AT COOLER STORAGE RING IN LANZHOU

The commissioning of the cooler storage rings (CSR) was successful, and the facility provides new possibilities for atomic physics with highly charged ions. Bare carbon, argon ions, were successfully stored in the main ring CSRm, cooled by cold electron beam, and accelerated up to 1 GeV/u. Heavier ions as Xe44+ and Kr28+ were also successfully stored in the CSRs. Both of the rings are equipped with new generation of electron coolers which can provide different electron beam density distributions. Electron-ion interactions, high precision X-ray spectroscopy, complete kinematical measurements for relativistic ion-atom collisions will be performed at CSRs. Laser cooling of heavy ions are planned as well. The physics programs and the present status will be summarized.

The stripper design and test at HIRFL-CSR

Charge stripping is employed to produce multi-charged ions for injecting the cooling storage ring After penetrating through the carbon foil, the widened distribution of ion charge states poses a limit to the ion injection Therefore, the carbon foil plays a key role in the charge snipping injection In this paper, foul strippers for Heavy Ion Research Facility at Lanzhou (HIRFL) and Cooling Sun age Ring (CSR) are introduced The charge state distribution of the stripped ions is measured and the stripping efficiency of the foils is investigated The experimental results are consistent with the theoretical values

Electron impact excitation rate coefficients of N II ion

This paper calculates the electron impact excitation rate coefficients from the ground term 2s(2)2p(2) P-3 to the excited terms of the 2s(2)2p(2), 2s2p(3), 2s(2)2p3s, 2s(2)2p3p, and 2s(2)2p3d configurations of N II. In the calculations, rnulticonfiguration Dirac-Fork wave functions have been applied to describe the target-ion states and relativistic distorted-wave calculation has been performed to generate fine-structure collision strengths. The collision strengths are then averaged over a Maxwellian distribution of electron velocities in order to generate the effective collision strengths. The calculated rate coefficients are compared with available experimental and theoretical data, and some good agreements are found for the outer shell electron excitations. But for the inner shell electron excitations there are still some differences between the present calculations and available experiments.

Theoretical study of the 4d photoabsorption of the Cs+ ion

Calculations of the 4d absolute photoabsorption cross sections of the Xe-like Cs+ ion covering the energy region from 80 to 190 eV have been performed by using the multi-configuration Dirac-Fock method. The calculated cross sections are compared with the absolute experimental photoabsorption cross-section spectrum (Kjeldsen et al 2002 J. Phys. B: At. Mol. Opt. Phys. 35 2845) and other available theoretical results. In the 80-90 eV region, the discrete structure resulting from photoexcitation of a 4d electron into nf and np orbits are successfully identified. Above the 4d threshold, i.e. in the 90-190 eV energy region, a reasonable agreement between experiment and computations is found for the intense 4d -> epsilon f shape resonance.

X-ray spectrum emitted by the impact of Xe-129(q+) on Mo surface

We studied the characteristic X-ray spectra produced by the interaction of highly charged ions of X-129(q+) (q =25, 26, 27) with surface of metallic Mo. The experimental result shows that highly charged ions can excite the characteristic X-ray spectra of L-shell of Mo when the beam' s intensity is not more than 120 nA. The X-ray yield of single ion reaches a quantitative level of 10(-8) and increases with the increment of the ion' s kinetic energy and ionic charge (potential energy). By measuring the X-ray spectra of Mo-L alpha(1) the M-level lifetime of Mo atom is estimated by using Heisenberg uncertainty relation.

TIME-DEPENDENT DENSITY FUNCTIONAL STUDY OF MULTIELECTRON TRANSFER IN Cq+-Na-4 COLLISIONS

The process of multielectron transfer from a Na-4 cluster induced by highly charged C6+, C4+, C2+ and C+ ions is studied using the method of time-dependent density functional theory within the local density approximation combined with the use of pseudopotential. The evolution of dipole moment changes and emitted electrons in Na-4 isobtained and the time-dependent probabilities with various charges are deduced. It is shown that the Na-4 cluster is strongly ionized by C6+ and that the number of emitted electrons per atom of Na-4 is larger than that of Na-2 under the same condition. One can find that the detailed information of the emitted electrons from Na-4 is different from the same from Na-2, which is possibly related to the difference in structure between the two clusters.

近玻尔速度高电荷态离子与表面作用诱发的溅射离子能谱

近玻尔速度高电荷态离子在物质表面诱发的溅射离子能谱研究在理论和实验上尚是一片空白。本工作针对溅射离子能谱测量，设计、建立了一台径向位置灵敏127o柱形静电离子能谱仪。该谱仪结合位置灵敏探测器，克服了传统静电谱仪只能通过扫描电场单次、单能量点取谱的缺陷，实现了分段取谱——单次可获取宽为0.85Ec ≤ E ≤ 1.15Ec的能谱，极大提高了实验测量效率。利用该谱仪，首次获得了0.8至1.8倍玻尔速度Ar7，8，9+离子与金属铍靶和高定向性石墨靶碰撞产生的溅射离子能谱（入射角45o ，出射角135o）。结果表明：1）能谱分布很宽，其峰值位于130eV至600eV之间，远大于线性级联碰撞区的几到十几eV；且峰位随入射离子速度增加向高能方向略有移动。2）铍靶的溅射能谱呈一个极不对称的峰分布——高能部分有很长的尾巴，下降趋势服从E-n分布；其能谱与入射离子速度关联很大，小于vBohr时指数n与线性级联碰撞接近，而大于vBohr时非线性贡献明显。3）石墨靶的能谱峰位与入射离子动能、势能相关；其谱形在上升到最大值后均出现一个很宽的平台，表明该系列碰撞系统中，非线性效应占主导

高电荷态离子与固体表面作用的研究

高电荷态离子与固体表面相互作用研究不仅在原子结构和能级寿命，量子电动力学效应和等离子体物理等方面具有重要的基础研究价值，而且在表面分析和加工，短波辐射源开发等方面也有着潜在的应用价值。论文介绍了在兰州重离子加速器国家实验室ECR离子源上建成的用于高电荷态离子与固体表面作用研究的物理实验终端，研究了高电荷态离子与固体表面作用中的可见光和X射线发射以及高电荷态离子在固体表面引起的离子溅射产额和电子发射产额。研究了固体表面靶原子特征可见光谱和X射线的激发机制；分析了空心原子X射线谱的重要特征以及高电荷态离子动能沉积和势能沉积在表面离子溅射和表面电子发射中的作用

高电荷态离子与固体表面作用的离子溅射和电子发射的实验研究

高电荷态离子与固体表面相互作用的研究是目前国际上广受关注的热点研究领域之一。本论文详细介绍了在兰州重离子加速器国家实验室ECR离子源上建成的高电荷态离子表面物理实验平台；着重叙述了在实验平台上完成的高电荷态离子在固体表面引起的离子溅射和电子发射的研究。我们用初动能Ek=216～720keV的高电荷态Pb36+离子和初动能为Ek=144～288keV的Arq+（q =11～16）离子以不同入射角度(Ψ＝15º～80º)作用于Nb、Si和SiO2表面，通过研究离子溅射产额与入射离子初动能、势能（电荷态）和入射角度的关系，得到了以下结论：离子溅射产额与炮弹离子的势能沉积和动能作用有关；对Ar离子，电荷态从11增加到16时，离子溅射产额是随之增长的。而对Pb36＋离子，表面离子溅射产额随入射离子初动能的变化关系跟核阻止能损随入射离子初动能的变化关系是一致的，离子溅射产额与核阻止能损是线性相关的。认为高电荷态引发的表面离子溅射过程是势能沉积作用与线性级联碰撞过程协同作用的结果。我们还测量了Heq+(q=1,2, Ek=12keV～48keV)，Neq+(q=2～8, Ek=18～192keV)，Arq+(q=3～12, Ek=72keV)离子垂直作用于Si, W, Au表面产生的电子发射产额。得到了纯粹势能电子发射产额与入射离子势能的定量关系，势能电子产额随入射离子势能的增加而线性增加，势能每增加1eV，单离子电子发射产额增加0.0088（以初动能为42keV的Neq+入射到W表面为例）。势能电子发射增量跟靶的性质有关，W表面对势能变化的响应最剧烈，其次是Si表面。通过引入纯粹动能电子产额与电子能损的比值B分析和研究了动能电子发射，随着入射离子原子序数和初动能的增加，B因子有缓慢降低的趋势；B因子与靶材料密切相关，Au靶的B因子明显大于Si靶和W靶；我们还首次把B因子的研究扩展到高电荷态离子领域，认为B因子与入射离子的势能（电荷态）无关

低速高电荷态离子与微孔箔的相互作用研究

低速高电荷态离子与纳米微孔箔相互作用的研究无论在基础研究方面还是实际应用方面都扮演着重要的角色，因此在近年来受到了广泛的关注，成为一个研究热点。 论文介绍了在兰州重离子加速器国家实验室320kV高压电子回旋共振离子源（ECRIS）上新建成的表面物理实验终端；着重叙述了在该终端上开展的高电荷态离子与绝缘体纳米微孔箔相互作用的实验工作，包括高电荷态离子穿过微孔箔后的电荷态分布、角分布以及微孔箔的导向能力；系统的研究和讨论了（1）出射离子的电荷态分布；（2）出射离子产额的角度分布，具体内容有入射倾角、入射离子的动能、电荷态以及后表面带电对角度分布的半高宽度的影响；（3）微孔箔导向能力，具体内容有表征导向能力的临界角、入射离子的动能、电荷态的变化以及后表面带电对临界角的影响；（4）总的离子产额随入射离子束流强的变化情况。 实验结果表明，微孔箔对入射的低速高电荷态离子有明显的导向作用，出射离子的角度分布为对称分布，且超过97%的出射离子保持了入射时的电荷态；入射倾角、初始动能、初始电荷态以及微孔箔后表面带电与否等对离子产额角度分布的半高宽和临界角会产生影响；总的离子产额会随入射流强的变化出现拐点。论文还利用导向效应模型对实验中出现的各种现象进行了定性的解释，并对进一步深入研究该项课题提出了初步的设想

低能高电荷态离子与氦原子碰撞中的双电子过程研究

本工作采用散射离子位置灵敏探测和反冲离子飞摘．时问符合技术，在小于一300keV的能量范围内，研究了高电荷态Xe离子（q=15，17，19，21，23）与He原子碰撞中双电子转移截面与单电子转移截而比与入射离子电荷态的关系；研究了入射离子电荷态q＝4，5，6，7的等电荷态序列Cq＋、Nq＋、Oq＋、Neq＋与He原子碰撞中，电子转移截面比与入射离子原子序数的关系。对Xeq＋＋ He碰撞体系，主要研究了靶原子完全转移两个电子（σ2）与完全转移一个电子（σl）的截面比σ2／σl与入射离子电荷态的依赖关系。对靶原子双电子过程提出一步过程假定，修正了ECB模型。通过与已有绝对截面的比较，得到了很好的符合结果。使用修正模型计算的截面比解释了本实验的截面比测量结果。对等电荷态序列Cq＋、Nq＋、Oq＋、Neq＋与He原子的碰撞，主要研究了转移电离与单俘获截面比与入射离子原子序数的依赖关系。在统计模型的理论框架下，引入势能参数。Ω研究发现，等电荷序列的转移电离与单俘获截面比与碰撞系统的。有很强的依赖关系，说明单电子俘获形成的能量沉积是引起转移电离的主要因素。本工作还研究了势能参数几对碰撞系统的转移电离与双俘获之间的相互关系的影响。结果表明，。对转移电离和双俘获在靶原子双电子过程中的比率权重起着决定性作用。