Dissociative ionization cross sections of CO2 at electron impact energy of 5 keV

The dissociative ionization of CO2 induced by 5 keV electrons in two-body and three-body dissociative channels of CO2＋2 and CO3＋2 is identified by the ion-ion coincidence- method using a momentum imaging spectrometer. The partial ionization cross sections （PICSs） of different ionic fragments are measured and the results generally agree with the calculations made by a semi-empirical approach. Furthermore, the PICSs of the dissociative channels are also obtained by carefully considering the detection efficiency of the micro-channel plates and the total transmission efficiency of the time of flight system.     

低能电子离化氢原子的三重微分截面

运用修正后的BBK理论计算了入射能近阈值的情况下(E0=30、25、20、17.6和15.6 eV),共面等能、两个出射电子相对角取不同固定值时电子入射离化氢原子的三重微分截面(TDCS),所得结果与实验进行比较,符合较好.指出:对3C波函数进行索末菲参量的修正是成功的,这一修正使得BBK模型也能对入射能近阈值的低能(e,2e)过程给出很好的描述.     

Cross sections for K-shell ionization of Si and Ar by 4 keV to 10 keV electron impact

K-Auger electron emission of Si and Ar produced by 4 keV to 10 keV electrons was measured. Absolute yields were obtained by normalizing to the elastically scattered primary electrons. From the yields cross sections for K-shell ionization were deduced. The cross sections are in good agreement with the results of a fit formula for K-shell excitation in the whole range measured, while they agree with results of PWBA calculations including electron exchange in the Ochkur approximation only for the higher impact energies.     

能量范围从20ke到34kev的锆元素K壳层电离截面

用20～34keV能量的电子束轰击锆靶,从而测得锆元素的K壳层电离截面。这些数据是国际上首次报道。在实验中采用电子输运双群模型修正了由厚衬底产生的反射电子对计数的影响。同时用蒙特-卡罗EGS4程序计算了电子在质量厚度为24.3μg cm     

L-subshell ionization cross sections for Au,Pb, and Bi by 60–600 keV electron impact

TheL ₁-,L ₂- andL ₃-subshell ionization cross sections of Au, Pb and Bi by 60–600 keV electron impact have been determined from the measured x-ray production cross sections. The experimental results have been compared with the relativistic PWBA, the Binary Encounter Approximation (BEA) and the Kolbenstvedt Approximation (KA) calculations. These calculations, especially the relativistic PWBA, give good agreement with the experimental data for theL ₃-subshell. For theL ₁- andL ₂-subshells there are some deviations and these can explain the disagreement observed for theL _α/L _χ- andL _γ/L _χ intensity ratios.     

能量范围从20keV到34keV的锆元素K壳层电离截面

 用20~34keV能量的电子束轰击锆靶,从而测得锆元素的K壳层电离截面。这些数据是国际上首次报道。在实验中采用电子输运双群模型修正了由厚衬底产生的反射电子对计数的影响。同时用蒙特卡罗EGS4程序计算了电子在质量厚度为24.3mg/cm²的锆靶中的平均路径长度。     

能量范围从20keV到34keV的锆元素K壳层电离截面

用20~34keV能量的电子束轰击锆靶,从而测得锆元素的K壳层电离截面。这些数据是国际上首次报道。在实验中采用电子输运双群模型修正了由厚衬底产生的反射电子对计数的影响。同时用蒙特卡罗EGS4程序计算了电子在质量厚度为24.3mg/cm2的锆靶中的平均路径长度。     

Differential cross sections for ionization of laser-aligned atoms by electron impact

The first experimental data are given for (e,2e) ionization from laser-aligned atoms. A linearly polarized laser excited Mg atoms to the 31P? state prior to ionization by low energy electrons. The scattered and ejected electrons were detected in coincidence and the differential cross section determined for a range of alignment angles. An asymmetric coplanar geometry was used, with one electron fixed and the other detected at different angles. The data are compared to that from the spherically symmetric 31S? state. Significant differences are found, in both magnitude and angular distribution.     

Empirical model for electron impact ionization cross sections of neutral atoms

A simple empirical formula is proposed for the rapid calculation of electron impact total ionization cross sections both for the open- and closed-shell neutral atoms considered in the range 1≤ Z≤92 and the incident electron energies from threshold to about 10⁴ eV. The results of the present analysis are compared with the available experimental and theoretical data. The proposed model provides a fast method for calculating fairly accurate electron impact total ionization cross sections of atoms. This model may be a prudent choice, for the practitioners in the field of applied sciences e.g. in plasma modeling, due to its simple inherent structure.     

Differential and total ionization cross sections due to impact of swift heavy ions

In the present work, the Binary stopping power theory was used to calculate total ionization cross section and differential cross section for energy transfer from a swift heavy ion to the target electrons. The dependence on the projectile charge state is studied. The calculated values are compared with the experimental values collected from the literature.     

Total cross sections for electron scattering from sulfur compounds

The original additivity rule method cannot give good results for electron scattering from SO,SO2,SO2Cl2,SO2ClF,and SO2F2 molecules at low energy,because the electron-molecule scattering is simply reduced to electron-atom scattering.Considering the difference between the bound atom in a molecule and the corresponding free atom,the original additivity rule is revised.With the revised additivity rule,the total cross sections for electron scattering from these molecules are calculated over a wide energy range below 3000 eV and compared with the available experimental and theoretical data.A better agreement between them is obtained.     

Mn and Cu K-shell ionization cross sections by slow electron impact

Near the threshold energy, electron induced Mn and Cu K-shell ionization cross sections have been measured. Except for energies very close to threshold, the results are in good agreement with the semi-empirical formula of Green and Cosslett.     

Triple differential cross sections for the ionization of water by electron and positron impact

Triple differential cross section calculations for the ionization of several valence orbitals of the water molecule by electron and positron impact are reported. We found a very good agreement with the experimental data in case of the almost spherical 2A₁ orbital. By changing the projectile’s charge, significant differences were observed between the electron and positron TDCSs.     

快电子碰撞碳原子K-壳层电离的三重微分截面

利用3C、DS3C和S3C模型分别计算了共面非对称几何条件下快电子碰撞碳原子K-壳层电离的三重微分截面(TDCS),将S3C模型计算结果与其它理论结果和实验数据进行了比较.表明:内壳层电离的TDCS呈现出一强的recoil峰,对于某些参量,recoil峰甚至高于binary峰.这一点与外壳层电离过程不相同.S3C模型能够较好地描述这样的电离过程.?     

Calculations of electron impact ionization cross section for simple biomolecules: Formic and acetic acids

Cross sections for single electron-impact ionization of formic acid (HCOOH) and acetic acid (CH₃–COOH) are calculated using the binary-encounter-Bethe model in the energy range from the ionization threshold up to 4000 eV. The present results are compared with available experimental and theoretical data.     

Doubly-differential ionization cross sections of positron impact on argon

We report the first measurement of doubly-differential ionization cross sections for positron impact on argon atoms. Energy- and angle-resolved measurements of ejected electrons in time correlation with the produced and detected ions have been performed. Corresponding measurements with incident electrons were made for comparison. With positrons and electrons as primary particles of 100 eV energy and ejected electrons of 15 eV, our measurements were extended over electron-emission angles from 0 to 90. Lacking theoretical predictions for the doubly-differential ionization of argon, we compare our measured data with the theoretical doubly-differential ionization cross sections, calculated for positron and electron impact on hydrogen by Klar and Berakdar (Freiburg) [1]. The angular dependence of positron and electron cross sections for argon agrees well with the theory for hydrogen. In particular, we found that for small angles of electron ejection the cross section for positron impact ionization exceeds that for electron impact by an order of magnitude in accordance with the predictions of Klar and Berakdar.     

Velocity dependence of total Penning ionization cross sections

The velocity dependence of the total Penning ionization cross sections,σ(v), is measured in the thermal relative velocity region, using a time of flight method.σ(v) curves are reported for the collision systems He(2¹ S)/Ar, Kr, Xe, N₂, Hg, He(2³ S)/Ar, Kr, Xe, N₂, Hg, Ne(³ P _{2, 0})/Kr, Hg, and Ar(³ P _{2, 0})/Hg. In a qualitative discussion it is shown that all features of the measuredσ(v) curves may be explained within the frame of the theory of Penning ionization, allowing to extract information on the physical quantities governing the process: on the interaction potentialV(R) and on the transition probabilityW(R). A theoretical calculation for the He(2³ S)/Ar system shows good agreement with our experimentalσ(v) curve. On the basis of the present results earlier data onσ(v), and on absolute cross sections and rate constants obtained at certain relative velocity distributions are discussed.     

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.