低和中等电离度离子的电子碰撞电离截面的扭曲波计算

利用扭曲波Born交换近似方法计算了Ne⁺，…，Ne⁶⁺的电子碰撞电离截面，计算结果同实验和其他理论结果相一致.为满足实际应用需要，给出了高精度的拟合公式.还讨论了扭曲波Born交换近似方法对低电离度离子的适用性以及交换势的引进对计算结果的影响. 关键词：     

类钠离子的电子碰撞电离截面

利用相对论修正扭曲波玻恩交换近似,计算了8个类钠离子的电子碰撞直接电离和激发自电离截面.基于这些结果,给出了计算类钠等电子系离子(18≤Z≤39)直接电离和激发自电离截面的高精度拟合公式.计算结果与现有的实验值和其他理论值比较,相当一致 关键词： 电离截面 组态相互作用 扭曲波玻恩交换近似 拟合公式     

类氦离子的KLL双电子复合过程的相对论理论研究

在相对论多组态Dirac-Fock理论基础上，发展了计算双电子复合截面的程序.并以类锂C³⁺，Ar¹⁵⁺，Kr³³⁺和U⁸⁹⁺等离子为例，详细计算了共振双激发态1s2l2l′的辐射衰变率、Auger衰变率及相应的双电子复合截面.对于C⁴⁺，Ar^l6+和Kr³⁴⁺离子的结果与已有的计算和实验结果都能很好地符合；对于U⁹⁰⁺离子，则重点 关键词： 双电子复合 截面 MCDF     

State-selective radiative recombination cross sections of argon ions

The n-, (n,l)- and fine-structure level state-selective radiative recombinations (RR) cross sections of argon ions Ar¹⁸⁺,Ar¹³⁺,Ar⁷⁺ and Ar⁺ are obtained with the semi-classical Kramer formula, the relativistic self-consistent field (RSCF) method and the relativistic configuration interaction (RCI) method. It is found that for the highly charged ions with few electrons, the cross sections calculated with these three methods are in good agreement with each other. But as the number of electrons increases, the Kramer formula deviates from the RSCF and RCI results. For instance, when the energy of the incident electron is larger than 100 eV, the n-state selective cross sections of Ar⁷⁺ calculated from the Kramer formula are underestimated for more than 50%. The RSCF results are in general agreement with the RCI results. However, for the low charged ions, a clear distinction appears due to the strong configuration interaction, especially near the Cooper minimum. The n-resolved (n≤10) and total Maxwellian averaged rate coefficients are calculated, and the analytic fitting parameters are also provided.     

Relativistic calculations of electron-impact ionization for highly charged hydrogen-like ions

Electron-impact ionization cross-sections and rate coefficients of the 1s ground state for H-like C, O, Mg, Ar, Fe, Cu, As, Kr, Y, Mo ions with incident electron energies up to 15 times the ionization threshold energy have been systematically calculated by the relativistic distorted-wave Born exchange (DWBE) approximation. The comparison of the result with the experimental data, other theoretical calculations and recommended values shows the very good agreement. The influence from relativistic and the lowest order QED effect in the calculation is discussed. The calculated ionization cross-sections are fitted by empirical formulas. These fits can be readily integrated over a relativistic Maxwellian electron distribution function to obtain rate coefficient for plasma modeling.     

Al^q＋（q=0～12）的电子碰撞电离截面和速率系数

使用扭曲波玻恩交换(DWBE)近似计算Al^q (q=0～12)的电子碰撞电离截面和速率系数,其中电离截面的高能行为由Bethe系数决定。分析了计算数据随电离度的变化规律,并且与可得到的实验的和其他计算的数据进行了比较,表明结果可靠。     

Electron impact ionization of helium isoelectronic systems

The electron impact single ionization cross sections, on the helium isoelectronic He, Li¹⁺, B³⁺, C⁴⁺, N⁵⁺, O⁶⁺, Ne⁸⁺, Na⁹⁺, Ar⁺¹⁶, Fe²⁴⁺, Mo⁴¹⁺, Ag⁴⁵⁺, and U⁹⁰⁺ targets, are calculated modifying the simplified Bell (SBELL) model [Eur. Phys. J. D 46, 281 (2008)]. The results of the present analysis are compared with the available experimental and theoretical data. The modified SBELL (MSBELL) model, incorporating the ionic correction factor in it, produces excellent agreement with the experimental data and theoretical calculations for all the two-electron systems, neutral or ions. This model may be a prudent choice in plasma modeling due to its simple inherent structure.     

Spectres auger et sections efficaces d'ionisation de la couche L23 du magnésium et de l'aluminium sous impact de protons et d'ions lourds (10–100 keV)

A comparison of Auger structures observed on the energy distributions of secondary electrons emitted from Mg and A1 solid targets bombarded by either light particles (H⁺ and He⁺) or heavy ions (Ne⁺, Ar⁺, …) is presented. With incident protons, it essentially appears a broad peak corresponding to a L₂₃VV transition and a weak shoulder due to the surface and bulk plasmon excitation. The Auger structures obtained with heavy ions are richer and the peaks which compose it are sharper. Such atomic-like structures correspond to Auger transitions from excited (with one or two L₂₃ holes) moving recoiling atoms. The experimental L₂₃ Mg and A1 ionization cross sections were determined from Auger spectra. In H⁺?Mg (or A1) collisions our results are in good agreement with the theoretical values calculated in a PWBA model. In the case of heavy ion-target interactions, we compared the experimental measurements with ionization cross section calculations obtained in a Landau-Zener model.     

Electron impact total ionization cross sections of beryllium and boron isoelectronic ions

A simple user-friendly empirical formula is proposed to calculate the electron impact total single ionization cross sections of beryllium-like Be, B⁺, C²⁺, N³⁺, O⁴⁺, Ne⁶⁺, Fe²²⁺, Hg⁷⁶⁺, and U⁸⁸⁺ and boron-like B, C⁺, N²⁺, O³⁺, Ne⁵⁺, Fe²¹⁺, Kr³¹⁺, and Xe⁴⁹⁺ targets. A simplified and modified version of the Bell formula is used in the present model incorporating the ionic correction factor. The predicted ionization cross sections are compared with the available experimental and theoretical results. Excellent agreements are found for the incident energies ranging from threshold to 10⁶ eV considered herein. The presented results achieve a level of agreement that is better than the calculations from the existing theoretical methods and empirical models. Hence, this model may be an excellent choice, due to its simplicity, for the practitioners in the fields of applied sciences and technologies.     

Excitation-autoionization cross sections and rate coefficients for Ga-like ions

Detailed level-by-level calculations of cross sections and rate coefficients for electron impact direct and indirect ionization of ions belonging to the GaI isoelectronic sequence (ground 3d ¹⁰4s ²4p) have been performed. The cross sections are presented in the energy range near the threshold for the five ions Kr⁵⁺, Mo¹¹⁺, Xe²³⁺, Pr²⁸⁺ and Dy³⁵⁺. The rate coefficients are given for ions from Kr⁵⁺ to U⁶¹⁺ in the GaI sequence at seven electron temperatures (kT _e = 0.1E _I , 0.3E _I , 0.5E _I , 0.7E _I ,E _I , 2E _I and 10E _I , where E _I is the first ionization energy). The calculations include the contribution of direct ionization (DI) calculated using the Lotz formula approximation and the contributions of excitation-autoionization (EA) computed in the framework of the distorted wave (DW) approximation for the 4s-nl, 3d-nl and 3p-nl resonant inner-shell excitations. The ionization enhancement due to the EA channels is presented as a function of Z along the GaI isoelectronic sequence. The present results show the great importance of the EA processes; an ionization enhancement factor of up to 10 is predicted for instance for La²⁶⁺ (Z = 57) at electron temperature of coronal equilibrium maximum abundance.     

Electron capture by slow multiply charged Ar and Ne ions from atomic hydrogen

At collision energies below 15 keV total charge transfer cross sections have been measured for multiply charged Ar^ζ+(2≦ζ≦6) and Ne^ζ+(2≦ζ≦4) ions colliding with atomic hydrogen. A Wood discharge was used to provide a hydrogen target with a sufficiently high degree of dissociation. Results are compared with measurements performed at higher energies and with theoretical calculations. For ζ=2 cross sections in atomic hydrogen are much smaller than in the molecular case, for ζ>2 the ratio of these cross sections varies between 0.7 and 1.6.     

Ionization cross sections and rate coefficients for the ground state of AsI-like ions

Detailed level-by-level calculations of cross sections and rate coefficients for electron impact direct ionization and excitation-autoionization of AsI-like ions in the 3d ¹⁰4s ²4p ³ (⁴S_3/2) ground state have been performed. The cross sections are presented in the energy range near the threshold for the five ions Mo⁹⁺, Xe²¹⁺, Pr²⁶⁺, Dy³³⁺ and W⁴¹⁺. The rate coefficients are given for all the ions from Sr⁵⁺ to U⁵⁹⁺ in the AsI sequence at the seven electron temperatures (k T _e = 0.1E _I ,0.3E _I ,0.5E _I ,0.7E _I ,E _I ,2E _I and 10E _I , where E _I is the first ionization energy). The calculations include the contribution of direct ionization (DI) calculated using the Lotz formula approximation and the contributions of excitation-autoionization (EA) computed in the framework of the Distorted Wave (DW) approximation for the 4s ? nl, 3d ? nl and 3p ? nl resonant inner-shell excitations. The ionization enhancement due to the EA channels is presented as a function of Z along the AsI isoelectronic sequence. The present results show the great importance of the EA processes; an ionization enhancement factor of up to 6.5 is predicted for instance for Dy³³⁺ (Z = 66) at electron temperature of coronal equilibrium maximum abundance.     

高离化态类镍离子电子碰撞激发过程的相对论扭曲波理论研究

利用相对论扭曲波方法和新发展的研究电子碰撞激发过程的计算程序REIE06,系统计算了电子碰撞激发高离化态类镍Gd³⁶⁺和Rn⁵⁸⁺—U⁶⁴⁺(Z=86—92)离子从基态到4l(l=s,p,d,f)次壳层精细结构能级的碰撞强度和截面.研究了随等电子系列变化时,从基态到与X射线激光有关的3d⁹4p和3d⁹4d激发态能级的电子碰撞激发截面随Z的变化,讨论了强的组态相互作用对高离化态类镍离子截面的影响.通过对Gd³⁶⁺离子涉及X射线激光跃迁的相关能级电子碰撞激发速率系数的计算,分析了等离子体中电子温度对碰撞过程的影响.同时,目前部分计算结果与以往的理论结果进行了比较,得到了很好的一致性. 关键词： 电子碰撞激发 相对论扭曲波方法 高离化态类镍离子     

Electron impact ionization cross sections for Li-like Al ion in ground and excited states

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Cross sections and rate coefficients of transitions in He and He-like ions induced by collisions with heavy particles

An approach to calculating the exitation cross sections and rate coefficients for a wide class of transitions in atoms and ions induced by collisions with heavy charged particles in considered. Calculations were carried out in terms of the Born approximation in the impact parameter representation with the normalization and Coulomb repulsion (in the case of an ionic target). Transitions between levels in He and He-like ions without changes of the principal quantum number are considered for n=2–4. Fitting formulas are suggested for transition rate coefficients. Tables of cross sections and parameters of fitting formulas are given for He and C⁴⁺.     

Interaction of <Superscript>3</Superscript>He<Superscript>2+</Superscript> and Ar<Superscript>6+</Superscript> ions with acetylene,ethylene, and ethane molecules

Time-of-flight mass spectroscopy methods are employed for studying processes occurring during capture of electrons by ³He²⁺ and Ar⁶⁺ multiply charged ions with energy 6z keV (z is the ion charge) from C₂H _n molecules (n = 2, 4, 6) with different multiplicities of C-C bonds. Fragmentation schemes of the molecular ions formed in such processes are established from analysis of correlations of recording times for all fragment ions. The absolute values of the cross sections of capture of an electron and capture with ionization are measured, as well as the cross sections of formation of fragment ions in these processes. The absolute values of total capture cross sections for several electrons are determined.     

H<Superscript>+</Superscript><Emphasis Type="Bold">and He</Emphasis><Superscript>2+</Superscript> impact single and double ionization of lead

H⁺ and He²⁺ impact single and double ionization cross sections of ground state lead atoms have been calculated in the binary encounter approximation. Calculations of direct double ionization cross sections have been performed in the modified double binary encounter model. The accurate expressions of σ_ΔE (cross-section for energy transfer ΔE) and Hartree-Fock velocity distributions for the target electrons have been used throughout the calculations. Contributions to double ionization from Auger effect following ionization of inner shells have been considered in the present work. Our H⁺ impact single and double ionization cross sections are in good agreement with the experimental observations. In calculations of He²⁺ impact cross sections, the present theoretical approach shows limited success in the experimentally investigated region (50–350 keV amu^-1).     

Two-photon excitation/ionization of deep shells of multiply charged atomic ions

Absolute values and the shape of cross sections for two-photon one-electron excitation/ionization of the 1s shell of Ne⁶⁺ and Ne⁸⁺ ions, taking into account the relaxation of the atomic core in the field of resulting vacancies, are calculated. The many-particle stabilization of a deep vacancy in moving from a neutral atom to multiply charged ions is taken into account. The calculations are made for linear and circular polarizations of the incident laser beam. The results of the calculations are predictive.     

Structure and thermal stability of AgCu chiral nanoparticles

Theoretical studies of electron impact double ionization cross sections of Ne⁵⁺ and Ne⁶⁺ ions have been performed in the binary encounter approximation (BEA). Direct double ionization (DDI) has been investigated in the modified double binary encounter model. The K-shell ionization cross sections have been also calculated in the BEA to take into account the contributions to double ionization from the ionization-autoionization (IA) process. The effect of the Coulombic field of the target ion on the incident electron has been considered in the present work. Accurate expression of σ _ΔE (cross section for energy transfer ΔE) and the Hartree-Fock (HF) velocity distributions for the target electrons have been used throughout the calculations. The present results are in overall moderate agreement with the experimental observations. Possible reasons behind the discrepancies between the theory and the experiment have been discussed.