New semi‐empirical formulas for calculation of K‐shell ionization cross sections of elements from beryllium to uranium by proton impact

Experimental ionization cross sections for K‐shell by protons in target atoms from beryllium to uranium available in the literature from 1953 to 1999 (nearly 5400 values) are collected to deduce the semi‐empirical K‐shell ionization cross sections by fitting the experimental data normalized to their corresponding theoretical values based on the ECPSSR model which accounts for Coulomb deflection, Energy loss of the projectile, Perturbed Stationary State and Relativistic effects, as a function of the reduced velocity parameter. Our results are compared with the experimental data and with the ECPSSR values and reference ionization cross sections obtained by Paul and Sacher [H. Paul and J. Sacher, At. Data. Nucl. Data. Tables 1989 , 42, 105]. Copyright © 2010 John Wiley & Sons, Ltd.     

M X‐ray production cross sections for heavy elements by proton impact

We present in this paper, M‐shell ionization cross sections and M X‐ray production cross sections calculated within the Energy loss, Coulomb deflection, Perturbed Stationary State and Relativistic effects (ECPSSR) theory for elements with 72 ≤ Z ≤ 90 for protons with 0.1–4.0 MeV energy. Our results are compared to the plane wave Born approximation (PWBA) predictions, the relativistic plane‐wave Born approximation including corrections for binding and Coulomb deflection effect (RPWBA‐BC) results and the ECPSSR calculations from earlier works. On the other hand, semiempirical and empirical M X‐ray production cross sections are deduced from the polynomial fitting of the available experimental data collected from different sources. A comparison is made between the different sets of results. The differences between the above calculations and the experimental results are pointed out and discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Three dimensional (Z‐dependence), collective and individual semi‐empirical formulae for L X‐ray production and ionization cross section by protons impact within corrected ECPSSR theory and updated experimental data: a review

In this paper we propose a new three dimensional semi‐empirical formulae for the deduction of L X‐ray production and ionization cross sections by introducing the dependence on the atomic number of the target, noted as ‘Z‐dependence’. The data are also fitted collectively and separately (for each element) by analytical functions to calculate semi‐empirical cross sections. For this purpose, the corrected ECPSSR model (noted as eCPSSR) and the published experimental data of L_α, L_β and L_γ X‐ray production and L₁, L₂ and L₃ ionization cross sections in the period (1950–2014) are combined to calculate the semi‐empirical ones for a wide range of elements by proton impact. The semi‐empirical cross sections (for the three x‐rays lines L_α, L_β, L_γ and the three sub‐shells L₁, L₂, L₃) are then deduced by fitting the available experimental data normalized to their corresponding theoretical values (using the eCPSSR model) giving a better representation of the experimental data for the individual interpolation. At last, a comparison is made between the three semi‐empirical formulae reported in this work. Copyright © 2016 John Wiley & Sons, Ltd.     

N‐shell ionization cross sections by proton impact in the BEA

The N‐subshell ionizations cross sections of heavy elements by proton impact have been calculated in the binary‐encounter approximation. The momentum distribution of target electrons is taken into account by the use of the nonrelativistic and relativistic hydrogenic models and the Hartree–Fock–Roothaan and the relativistic Hartree–Fock–Roothaan methods. The obtained subshell ionization cross sections are compared with the experimental data and other theoretical calculations. The electronic relativistic effect and the wave‐function effect on N‐shell ionization cross sections are discussed.     

Generation of experimental L x‐ray fluorescence cross‐sections for inter‐elements at inter‐energies EL1 ≤ E ≤ EK (computer program IGELCS)

The experimental values of L x‐ray fluorescence (XRF) cross‐sections are not available for all the elements in the range La–U, at all the photon energies E in the range EL1 ≤ E ≤ EK. To generate L XRF cross‐sections, where experimental measurements are not available, two empirical relations have been developed, one between the L XRF cross‐sections and photon energy and the other between the L XRF cross‐sections and atomic number. For the measured data on L XRF cross‐sections at incident energies between Ll and K edges of an element and the data on L XRF cross‐sections for elements in the range 57 ≤ Z ≤ 92 at an energy value, polynomial fits have been derived. The L XRF cross‐section values generated with the derived empirical relations were found to be in agreement with the experimental values within their experimental uncertainties. Subsequently, a software code IGELCS was developed to interpolate and to generate the cross‐sections at inter‐energies and for inter‐elements in a single computer run. The running of the software requires minimum input data on five elements at five common energies. Copyright © 2003 John Wiley & Sons, Ltd.     

MEASUREMENTS OF Fe AND Cu K-Shell IONIZATION CROSS SECTIONS BY SLOW ELECTRON IMPACT

ＭＥＡＳＵＲＥＭＥＮＴＳＯＦＦｅＡＮＤＣｕＫ－ＳｈｅｌＩＯＮＩＺＡＴＩＯＮＣＲＯＳＳＳＥＣＴＩＯＮＳＢＹＳＬＯＷＥＬＥＣＴＲＯＮＩＭＰＡＣＴＬｉＴａｉｈｕａＡｎＺｈｕＬｕｏＺｈｅｎｇｍｉｎｇＣｅｎｔｅｒｆｏｒＲａｄｉａｔｉｏｎＰｈｙｓｉｃｓ，Ｉｎｓ...     

Electron-impact ionization cross sections and rates for ions of argon

A distorted-wave Born exchange (DWBE) approximation including relativistic correction is used to calculate the electron-impact ionization cross sections and rate coefficients for the highly charged ions Ar⁷⁺,…,Ar¹⁷⁺. The comparison of the calculated results with the experimental data and other theoretical calculations shows that the DWBE method is valid for these ions of argon. The calculated results for direct ionization cross sections and excitation autoionization were fitted by empirical formulas to meet the requirements of applications. A set of improved empirical formulas are used for the fast and accurate calculations of rate coefficients from the fit parameters of cross sections.     

8—9.5 keV正电子致Ti的K壳层电离截面的实验研究

低能正电子碰撞原子内壳层电离截面的实验数据目前还很缺乏,从而影响了对近年来发展的各相关理论模型的检验,限制了慢正电子束流技术在诸多领域中的应用.本文采用慢正电子束流装置产生的8—9.5 keV正电子束碰撞纯厚Ti靶,利用硅漂移探测器(SDD)收集正电子碰撞Ti靶产生的X射线,同时采用高纯锗探测器在线获得与靶碰撞的入射正电子数,从而得到Ti的K壳层实验产额,并基于蒙特卡罗模拟程序PENELOPE获得模拟产额.将实验产额分别与内壳层电离截面数据库采用经典光学数据模型(ODM)和扭曲波玻恩近似理论模型(DWBA)的蒙特卡罗模拟产额进行对比,发现基于ODM理论模型的模拟产额与实验值有较大的偏差,基于DWBA理论模型的模拟产额与实验结果符合较好.根据实验产额和基于DWBA理论模型的模拟产额的比较结果,对蒙特卡罗模拟程序使用的DWBA理论模型数据库进行修正后再进行模拟和比较,从而得到可靠的8—9.5 keV正电子致Ti原子K壳层电离截面数据.     

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.     

质子碰撞电离氖原子的理论研究*

利用连续扭曲波方法（CDW）和初态程函近似-连续扭曲波方法（CDW-EIS）对质子碰撞电离氖原子 壳层随电离电子能量的单重和二重微分散射截面及总截面进行了计算,与实验数据进行了比较,详细分析了曲线结构,比较了模型之间的差异,研究了初态程函近似对单重和二重微分散射截面的影响,并对其内部碰撞电离机制进行了探讨.研究发现,初态程函近似对各壳层电离截面有较大影响,这种影响随着入射质子能量的增大而越来越小.     

Measurements of the surface ionization in multilayered specimens

Results from experimental measurements of surface ionization, Φ(0), from multilayered specimens are presented. The studied samples consisted of Cu and C layers of different thicknesses, deposited on single‐element substrates that cover the periodic system, from Be to Bi. The surface ionization was determined by the tracer method, i.e. by measuring the characteristic x‐ray intensity emitted from an ultra‐thin tracer layer deposited on the multilayer structure and, according to Castaing's definition, dividing it by the x‐ray intensity from an equivalent, self‐supporting tracer layer. The considered tracer element was Ni, and measurements were performed for Ni Kα and Ni Lα x‐rays. Experimental results are compared with Monte Carlo simulation results generated by using the general‐purpose simulation package PENELOPE with ionization cross‐sections computed from an optical‐data model. Measured data are also compared with the predictions of an empirical analytical expression for Φ(0), which was derived from systematic Monte Carlo simulations. Copyright © 2004 John Wiley & Sons, Ltd.     

Cq+ 和Oq+与原子碰撞的电子俘获过程的理论研究

在ECPSSR理论的基础上， 利用OBKN近似描述电子俘获过程， 得到了包括电子俘获过程贡献的ECPSSR理论， 编写了相应的计算程序。 采用该程序计算了不同电荷态离子与多种靶原子碰撞的电子俘获截面和相应的X 射线产生截面， 将计算得到的包含电子俘获过程贡献的X 射线产生截面与实验结果进行了比较。 对于具有满K壳层的入射离子碰撞， X 射线产生截面与入射离子电荷态基本无关； 对于以直接电离为主导的碰撞过程， 计算得到的X 射线产生截面与实验数据符合得很好； 对于全裸和单K空穴入射离子的碰撞， 计算高估了X 射线产生截面。 Based on the ECPSSR theory, the contribution of the electron capture is described by the OBKN theory. The cross sections of electron capture and X ray production for the collision of different charge state projectiles with various targets are calculated, and compared with the available experimental data. It is found that the obtained X ray production cross sections are almost independent of the projectile charge states for projectiles without a K vacancy. For the collision processes of direct ionization, the present calculated results agree well with the experimental data. The calculations overestimate the X ray production cross sections for the projectiles with full and a K vacancy.     

A semi-empirical formula for total cross sections of electron scattering from diatomic molecules

A fitting formula based on the Born approximation is used to fit the total cross sections for electron scattering by diatomic molecules (CO, N₂, NO, O₂ and HCl) in the intermediate- and high-energy range. By analyzing the fitted parameters and the total cross sections, we found that the internuclear distance of the constituent atoms plays an important role in the e-diatomic molecule collision process. Thus a new semi-empirical formula has been obtained. There is no free parameter in the formula, and the dependence of the total cross sections on the internuclear distance has been reflected clearly. The total cross sections for electron scattering by CO, N₂, NO, O₂ and HCl have been calculated over an incident energy range of 10–4000 eV. The results agree well with other available experimental and calculation data.     

电子与多电荷离子的碰撞电离(英文)

主要揭示了不同电离机制对高电荷态离子单电离和多重电离的贡献 ,包括直接电离 (一步过程 )、激发 自电离 (两步过程 )以及内壳Auger过程 ,研究了高电荷态镨离子的电子碰撞电离. Electron-impact ionization of ions is one of the most fundamental processes in every kind of plasma. Especially in high-temperature plasmas-whether in laboratory (nuclear fusion) or in astrophysics (atmosphere of stars)-atoms become ionized into multiply-charged ions by electron impact. The main purpose of our investigations is to unravel the contributions from different ionization mechanisms-like direct ionization (one-step process), excitation-autoionization (two-step process) and...     

Inner-shell ionization of atoms by electron,positron and photon impacts

Plane wave Born approximation with Coulomb, relativistic and exchange corrections is employed to obtain L1-, L2- and L3-subshell ionization cross sections of several atoms due to electron and positron impacts for projectile energy varying from the threshold of ionization to 60 times the threshold energy. Photoionization cross sections for all the three L-subshells of the atoms are also calculated using the hydrogenic approximation for the atomic wave functions. For L3-subshell the present cross sections due to electron impact are in good agreement with a number of experimental data for different atoms over the entire energy range investigated. For L1- and L2-subshells the present calculations yield qualitative agreement with the experimental data. The agreement between the present results and the limited experimental data for positron impact is also satisfactory. The hydrogenic approximation for the L-subshell photoionization is found to be good at small photon energies but it underestimates the cross sections at large photon energies.     

Physical parameters for atomic inner‐shell photoionization processes and analytical applications: a status report

The atomic inner‐shell vacancy decay processes comprising of radiative and non‐radiative transitions are characterized by the physical parameters, namely, the photoionization cross‐sections; X‐ray, Auger and Coster–Kronig (CK) transition rates; fluorescence and CK yields; and the vacancy transfer probabilities. These parameters are required to calculate the K‐shell and L_i (i = 1–3)/M_i (i = 1–5) sub‐shell X‐ray production cross‐sections and relative intensities which, in turn, are needed for different analytical applications. This report intended to provide a detailed account of the currently available data sets of different physical parameters for use in various analytical applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Antikaon production in nucleon- nucleon reactions near threshold

The antikaon production cross section from nucleon-nucleon reactions near threshold is studied in a meson exchange model. We include both pion and kaon exchange, but neglect the interference between the amplitudes. In case of pion exchange the antikaon production cross section can be expressed in terms of the antikaon production cross section from a pion-nucleon interaction, which we take from the experimental data if available. Otherwise, a K* -resonance exchange model is introduced to relate the different reaction cross sections. In case of kaon exchange the antikaon production cross section is related to the elastic KN and K?N cross sections, which are again taken from experimental measurements. We find that the one-meson exchange model gives a satisfactory fit to the available data for the NN → NN KK? cross section at high energies. We compare our predictions for the cross section near threshold with an earlier empirical parameterization and that from phase space models.     

Measurement of Titanium and Manganese K -shell Ionization Cross Sections by Electron Impact

报道了电子引起的钛、锰原子的Ｋ壳层电离截面实验值。实验中,采用了薄靶厚衬底技术,并将衬底中反射的电子对测量值的影响进行了修正。实验结果与其他文献报道的测量结果相吻合。最后,还将实验结果与Ｃａｓｎａｔｉ等人的经验公式进行了比较。     

光电离过程中Fe靶和V靶特征辐射的角相关研究

在发射角120°—170°的范围内,应用硅漂移探测器以10°为间隔对中心能量为13.1 keV的韧致辐射诱发Fe靶和V靶发射的典型K系X射线光谱进行了测量.得到特征X射线Kα和Kβ的特征谱线,考虑探测器对特征X射线的探测效率、靶对入射光子和出射光子吸收的校准及大气对特征X射线的吸收后,结果显示不同探测角度下Kβ与Kα的强度比为一常数.将本次实验探测角度为150°时的Kβ/Kα强度比值的实验值、理论计算值和Ertuğral的实验结果进行对比,发现实验结果与预期相符.对比不同探测角度下的强度比变化趋势推断特征X射线的角度依赖关系,分析认为Kα和Kβ在探测范围内是各向同性发射的.     

中子与63,65Cu反应的理论计算

根据中子与天然Cu及其同位素反应的总截面, 去弹截面和弹性散射角分布的实验数据, 得到中子的光学模型势参数; 应用得到的光学模型势参数, 光学模型, 统一的Hauser-Feshbach和激子模型理论, 以及扭曲波玻恩近似理论, 系统计算和分析了中子与^63,65Cu反应的非弹散射角分布和双微分截面, 理论结果与实验很好的一致.