Electron impact ionization of Zn+ and Ga+

We have investigated the contribution of excitation-autoionization to the electron impact ionization of Zn⁺ and Ga⁺ using the binary encounter approximation. Hartree-Fock velocity distributions for the bound electrons have been used throughout the calculations of direct and indirect ionization cross-sections. The calculated cross-sections are in good agreement with recent experiments. We have also compared our results with other theoretical calculations.     

Electron impact ionization of Ba,Ba+ and Ba2+

The binary encounter approximation has been used to investigate the effect of charge state of the target atom (ion) on the electron impact excitation autoionization cross-sections. Roothan-Hartree-Fock (RHF) velocity distribution for the bound electrons has been used through-out the calculations. The present results give a good account of the experimental observations.     

Electron impact single and double ionization of halogens

The binary encounter approximation has been used for calculations of electron impact single ionization cross-sections for F, Cl, Br and I and double ionization cross-sections for Br and I. Contributions of ionization from inner shells have also been included in the calculations. Hartree-Fock momentum distribution has been used for the bound electron as far as possible. The results have been found to be in satisfactory agreement with experimental observations.     

Electron impact double ionization of Ba and Ba+

Electron impact double ionization cross-sections for Ba and Ba⁺ have been calculated in the binary encounter approximation. Hartree-Fock velocity distribution has been used for the first ejected electron and a hydrogenic velocity distribution for the second. For Ba⁺ the focusing effects of the target ion on the incident electron have been incorporated in the calculations. Contributions from ionization-autoionization to the ionization cross-sections, as observed in experiments, have been included in the present work. The calculated results show structures as observed in recent experiments.     

Electron impact single and double ionization of magnesium

Electron impact single and double ionization cross-sections for magnesium have been calculated in the binary encounter model using accurate expression for (cross-section for energy transfer ΔE) as given by Vriens. Hartree-Fock velocity distributions for the target electrons have been used throughout the calculations. In case of double ionization contributions of inner shell ionization and Auger emission have been included in the present work. The results obtained in case of single ionization are excellent and at the same time the double ionization cross-sections show reasonably good agreement with the recent experimental observations. Substantiation of the viewpoint of Peach, and Boivin and Srivastava that a vacancy in the 2p shell of magnesium leads to double ionization is a remarkable feature of the present investigation. Received 9 October 2001 / Received in final form 8 January 2002 Published online 28 June 2002     

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

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Single and double ionization of gallium by electron impact

Electron impact single and double ionization cross sections of gallium have been calculated in the binary encounter approximation using accurate expression for σ_Δ;E including exchange and interference as given by Vriens and Hartree-Fock velocity distributions for the target electrons throughout the calculations. It is concluded that the ionization of 3d shell contributes partly to single ionization and partly to double ionization. The results so obtained show reasonably good agreement with the experimental data.     

Electron impact ionization of large krypton clusters

We show that the detection of ionization of very large van der Waals clusters in a pulsed jet or a beam can be realized by using a fast ion gauge. Rapid positive feedback electron impact ionization and fragmentation processes, which are initially ignited by electron impact ionization of the krypton clusters with the electron current of the ion gauge, result in the appearance of a progressional oscillation-like ion spectrum, or just of a single fast event under critical conditions. Each line in the spectrum represents a correlated explosion or avalanche ionization of the clusters. The phenomena have been analysed qualitatively along with a Rayleigh scattering experiment of the corresponding cluster jet.     

Electron impact single ionization of mono- and di-positive ions

The electron impact ionization cross-sections of mono- and di-positive ionic targets are calculated using a second version of the modified binary-encounter-dipole (MBED) model, previously reported [M A Uddinet al, J. Phys. B37, 1909 (2004)]. The present version differs from the previous one in the scale factor of the Burgess denominator and is applicable to targets with chargesq = 1 and 2. The MBED in the present form is found to work well for 11 ionic targets ranging from Be⁺ to K⁺ and complements its previous version valid for targets withq s> 2     

Electron correlation in fast ion-impact single ionization of helium atoms

A four-body distorted-wave approximation is applied for theoretical analysis of the fully differential cross sections(FDCS)for proton-impact single ionization of helium atoms in their ground states.The nine-dimensional integrals for the partial amplitudes are analytically reduced to closed-form expressions or some one-dimensional integrals which can be easily calculated numerically.Calculations are performed in the scattering and perpendicular planes.The influence of the target static electron correlations on the process is investigated using a number of different bound-state wave functions for the ground state of the helium targets.An illustrative computation is performed for 75-ke V proton–helium collisions and the obtained results are compared with experimental data and other theoretical predictions.Although for small momentum transfers,the comparison shows a reasonable agreement with experiments in the scattering and perpendicular planes,some significant discrepancies are still present at large momentum transfers in these planes.However,our results are compatible and for some cases,better than those of the other sophisticated calculations.     

Electron impact ionization of SiCl<Subscript>2</Subscript> and SiCl

We measured absolute partial cross sections for the formation of all singly charged positive ions produced by electron impact on SiCl₂ and SiCl from threshold to 200 eV using the fast-neutral-beam technique. Some of the cross section curves exhibit an unusual energy dependence with a pronounced low-energy maximum at an energy around 30 eV, which may be indicative of the presence of indirect ionization channels. Dissociative ionization channels are dominant for both species. The experimentally determined total single ionization cross sections for both species agree very well with calculated cross sections using the Deutsch-M?rk (DM) formalism. A brief summary of the ionization cross sections determined for all four SiCl_x (x=1–4) species is given highlighting similarities and differences.     

BrCl分子近域轨道的电子动量谱学研究

Bromochlorodifluoromethane(CF2BrCl),also knownasHalon1211inindustry,isamainagent widelyusedforfiresuppressionapplicationsandhas receivedconsiderableattentionbecauseofitspotential forstratosphericozonedepletion[1,2].Thedetailed informationonpropertiesofCF2BrClmoleculesuchas ionizationpotential,chemicalbondingcharacterand electrondensitydistributionofmolecularorbitals,especiallyofthefrontiermolecularorbitals,isbelieved tobeimportantforchemicalreactionandpossible molecularrecognitionaccordingt…     

Electron impact optical excitation of helium-like ions in Coulomb-Glauber approximation

The Coulomb-Glauber approximation is applied to evaluate the electron-impact excitation integrated cross sections for 1¹ S —n ¹ P (n=2, 3) transitions in helium-like ions, C⁴⁺, N⁵⁺, O⁶⁺ and Ne⁸⁺. The results are presented in terms of scaled collision strengthn ³ Z ² k _i ² σ and scaled integrated cross-sectionZ ⁴σ. Our values when compared with other available theoretical results are found to be larger than the Coulomb-Born and distorted wave polarised orbital (DWPO) values.     

环己烯分子2b和3a轨道的电子动量谱学研究

报道了环己烯(C6H10)分子2b和3a轨道电子动量谱的首次研究,并且给出了价轨道的电离能谱信息,实验在非共面对称几何条件下的能量多道型电子动量谱仪下完成,入射电子的能量为1200eV加结合能.通过Hartree-Fock和密度泛函方法计算得到了C6H10分子2b和3a轨道的动量谱,在动量大于0.25a.u.区域理论与实验结果符合较好,实验结果与理论计算相比在低动量端出现“上翘”的现象,这可能是由于分子的扭曲波效应引起的.     

Electron impact ionization of diatomic molecules

Cross sections for the ionization of N₂, CO and O₂ diatomic molecules by electron impact are calculated. The applied distorted wave model is based on our previous studies for positron impact, the molecular orbitals being described by Gaussian wavefunctions. Our study emphasizes the importance of electron exchange and of using correct distorted waves for the ejected electron.     

Double-hump resonance structure of the cross sections for electron impact ionization of Ar5+

Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar5+. Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute up to 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the cross sections is demonstrated and the contributions of metastable states are also taken into account.     

CFCl3分子2e和4a1轨道的电子动量谱研究

由于工业的迅速发展 ,使得空气质量急剧下降 ,因此对影响大气的分子进行深入研究变得非常必要 .本实验室已经对影响环境的甲烷[1] 、丙烷[2 ] 、CO2 [3] 等分子进行了电子动量谱研究 ,为环保提供了有用的数据 .CFCl3作为工业广泛应用的气雾剂和制冷剂原料 ,它的大量使用导致了大气中臭氧的减少[4 ] .前人已用光电子谱学的方法[5- 8] 研究了CFCl3,我们又用电子动量谱的手段对CFCl3分子进行了进一步的研究 ,即从波函数的层次上详细了解CFCl3的电子结构 .(e ,2e)电子动量谱学在研究分子的电子结构方面有非常独特的优越性[9- 12 ] ,它可以…     

共面双对称条件下电子碰撞Ar原子单电离的一阶扭曲波Born近似

在共面双对称几何条件下,利用一阶扭曲波Born近似计算了中低能电子碰撞Ar原子(3p壳层电子)单电离的三重微分截面,并与最近的实验数据做了比较.结果表明,对于Ar原子,当入射电子能量比电离阈高40 eV以上,随着入射能量的增加,binary和recoil碰撞机理逐渐占据支配地位;在近阈能量范围,上述碰撞机理不再处于支配地位,扭曲效应明显.要完备地描述中低能入射条件下Ar原子的电子碰撞电离过程,理论模型必须同时考虑多种散射机理.     

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.     

激光金等离子体的电子离子碰撞电离速率系数

电子离子碰撞电离过程在超组态碰撞辐射(SCROLL)模型中真实模拟非局域热动力学平衡(non-LTE)高Z材料Au激光等离子体M带谱5f-3d跃迁中各种复杂离子的电离态特性,诸如离子的平均电离度和电荷态分布是一个主要过程.基于准相对论扭曲波玻恩交换近似,采用组态平均的方法,从头计算了金M带类铁金离子-类锗金离子的电子离子碰撞电离速率系数,其中电离截面的高能行为由Bethe系数决定.结果表明:在"神光Ⅱ"实验装置诊断的电子温度～2keV,电子密度～6×1021cm-3范围内,这些参数有利于使用超组态碰撞辐射模型拟Au的激光等离子体M带细致谱5f-3d跃迁的平均电离度和电荷态分布.