电子引起的钛和锰的K壳层电离截面测量

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。     

K-shell ionization of Si,Ti, Cu and Ag for incident protons,4He and14N ions in the energy range of 0.17–2.0 MeV/amu

K-shell X-ray production cross sections of Si, Ti, Cu and Ag were measured for incident protons,⁴He and¹⁴N ions in the energy range of 0.17≦E ₁/A ₁≦2 MeV/amu. The experimental ionization cross sections are compared with calculations according to the simple Plane Wave Born Approximation (PWBA) theory as well as the corrected PWBA model (PWBABC). Strong deviations of the experimental cross sections from theZ ₂ ¹ scaling are observed and discussed quantitatively.     

L-shell vacancy production in Ag,Ta and Au for incident ionsZ 1≦10 in the energy range of 0.125–4 MeV/amu

Absolute Ag, Ta and AuL-shell X-ray cross sections were measured using protons,⁴He,¹⁴N as well as²⁰Ne ions in the energy range of 0.125–4 MeV/amu. By means of single-hole fluorescence yields experimental ionization cross sections were deduced and compared with calculations according to the corrected PWBA model — PWBA(BPCR). With decreasing asymmetry of the collision system the experimental cross sections exceed the predictions of the direct ionization theory. This is caused by an increasing contribution of a competing KL charge exchange mechanism which was investigated in detail for Ne+Ag. The Lapicki and Losonsky capture model was found to fail at energiesE<1 MeV/amu because adiabatic relaxation effects in the projectileK-shell become important. An estimation by means of the Nikitin model led to more physically comprehensible results at the lowest ion velocities investigated.     

Calculation of Absolute Outer-Shell Electron Impact Ionization Cross Sections

The recently developed semiempirical DM-approach for the calculation of electron impact single ionization cross sections is applied here to the ionization of the rare gases (Ne, Ar, Kr and Xe) via ejection of an outer s-shell electron. The results obtained are compared with previous experimental and theoretical s-shell ionization cross section functions.     

Ionization for Hf- and W-L-shell by electron impact

Electron-induced Hf-, W-L-shell partial, total production cross sections, mean ionization cross sections and Hf-L_3-shell ionization cross sections (at two energies) have been measured as functions of electron energies (from near threshold to 36keV). The influence of electrons reflected from the backing of the thin targets on measured results was corrected using a model to relate to the electron transport process. The mean paths of electron multi-scattered in the target itself (including forward and backward scattering) were calculated by means of Monte Carlo program (EGS4) and they were used to correct measured results. A comparison with both theoretical predictions was given.     

K-shell ionization by protons for Cr,Cu, In and by alpha-particles for Cr,Cu

K-shell ionization cross sections have been determined for Cr, Cu and In at proton bombardment in the energy region from 0.9 to 2.5 MeV. The same cross sections were determined for Cr and Cu at alpha bombardment in the 0.9–4.0 MeV region. The experimental results are compared with five different theoretical calculations.     

K-shell ionization by protons for Cr, Cu, In and by alpha-particles for Cr, Cu

K-shell ionization cross sections have been determined for Cr, Cu and In at proton bombardment in the energy region from 0.9 to 2.5 MeV. The same cross sections were determined for Cr and Cu at alpha bombardment in the 0.9–4.0 MeV region. The experimental results are compared with five different theoretical calculations.     

Inner-shell ionization created by fluorine ions in nearly symmetric collisions

We have measured projectile and target X-ray cross sections for F + Si, S, Ar and Kr collisions at projectile energies from 1 to 25 MeV. The experiments were performed under single collision conditions using a differentially pumped gas target. X-rays were measured by a Si(Li) detector and a proportional counter. The experimental cross sections are compared to predictions of theoretical models for direct and quasi-molecular ionization. Effects of multiple ionization that influence theK-shell fluorescence yields were examined using experimental information from line energy shifts and intensity ratios.     

K-shell X-ray production for fluorine ions on target elements Ti to La

The production of target atomK-shell X-rays has been studied for 2 to 28 MeV fluorine ions incident on thin solid targets of 14 elements with atomic numbers Z₂=22 to 57. Total X-ray production cross sections, energy shifts ofK _α andK _β lines andK _α/K _β intensity ratios were measured with a Si(Li) detector. The results of cross section measurements are compared with theoretical predictions of inner shell ionization. In most cases, satisfactory agreement between measured cross sections and theoretical Coulomb ionization cross sections, corrected for the perturbation of the target atom by the projectile charge and for relativistic effects, was obtained.     

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.     

Search for the density effect in inner-shell lonization by ultra relativistic electron impact

We have extended the measurements ofK-andL-shell ionization cross sections by electron impact into the ultra relativistic energy region, 0.9≦E≦2.0 GeV, in order to search for a saturation of the cross section. This phenomenon, which is due to the polarization of the target medium, is called density effect. It is predicted to occur at several hundred MeV impact energy and preferentially for lowZ target elements. Theoretical calculations are presented, based on the one-photon-exchange approximation. The absolute measurements of theK-andL-shell cross sections for Ni(K), Cu(K), Ag(K, L) and Au(L) performed at the 2.5 GeV electron synchrotron of the Bonn University, however, exhibit that the cross sections show no saturation but are still increasing. Furthermore, from theK X-ray yields, obtained at 0.9 and 2.0 GeV by bombarding the lowZ elements S, Ca, Mn, Ni and Ge, we obtain for the corresponding cross section ratio σ _K (2GeV)/σ _K (0.9GeV)=1.08±0.01 on the average. TheK X-ray yield of a composite Ca — Mn target amounts to $$[\sigma _K (Ca;2.0GeV)/\sigma _K (Mn;2.0GeV)]/[\sigma _K (Ca;0.9GeV/\sigma _K (Mn;0.9GeV)] = 0.99 \pm 0.02.$$ . All three results are in disagreement with theory. This severe discrepancy is discussed but the origin for it is not yet understood.     

Inner-shell ionization ofZ=25–32 elements by 5-48 MeV32S ions

TheK-shell ionization cross sections of Mn, Ni, Cu, Zn and Ge under³²S bombardment have been measured in the energy range from 5 to 48 MeV. The cross sections are compared with available theories based on a direct Coulomb ionization mechanism and with the predictions of theK-vacancy sharing process. This last process can reasonably account for the measured cross sections at high bombarding energies. The energy shifts of theK _α- andK _β-lines and theK _α/K _β-intensity ratios have also been measured. This information is used to deduce the defect configuration of the atoms. The mechanisms responsible for the multiple vacancy production are discussed.     

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

ＭＥＡＳＵＲＥＭＥＮＴＳＯＦＦｅＡＮＤＣｕＫ－ＳｈｅｌＩＯＮＩＺＡＴＩＯＮＣＲＯＳＳＳＥＣＴＩＯＮＳＢＹＳＬＯＷＥＬＥＣＴＲＯＮＩＭＰＡＣＴＬｉＴａｉｈｕａＡｎＺｈｕＬｕｏＺｈｅｎｇｍｉｎｇＣｅｎｔｅｒｆｏｒＲａｄｉａｔｉｏｎＰｈｙｓｉｃｓ，Ｉｎｓ...     

Proton and α-particle impactM-shell ionization of atoms in binary encounter approximation

M-shell ionization cross sections for atoms due to the impact of proton and α-particles have been calculated in the binary encounter approximation. The effects of Coulomb deflection of the incident projectile and increase in binding of the target electron have been investigated. Roothan-Hartree-Fock velocity distribution for the target electrons has been used in the present work. The calculated cross-sections have been compared with experimental results and other theoretical calculations wherever available. The present calculations give a good account of experimental observations.     

SEMI‐empirical and empirical formulas for calculation of K‐shell ionization cross sections by proton impact: a comparison

According to the plane wave Born approximation (PWBA) and the binary encounter approximation (BEA) models, it is possible to fit the cross sections obtained with any atomic element at any particle energy using a scaling law for a K‐shell. The semi‐empirical K‐shell ionization cross sections are then deduced by fitting the available experimental data normalized to their corresponding theoretical values. For the empirical K‐shell ionization cross sections, a third‐order polynomial was used to fit the same experimental data for protons. Our results are compared with the predictions of the ECPSSR theory and with other earlier works. Good agreement is obtained, but it is emphasized that the ultimate solution is to deduce the cross sections by fitting the available experimental data for each element separately. Copyright © 2008 John Wiley & Sons, Ltd.     

Al,Ti,Cu,Mo原子的K壳层电离截面的理论计算

 电子离子碰撞过程是模拟激光等离子体的超热电子的能谱和产额的主要过程之一。基于相对论性的电子离子碰撞的K壳层的电离截面理论,计算了Al,Ti,Cu,Mo原子的K壳层的电子离子碰撞截面,结果和最近的文献实验数值和其它理论数值进行了比较,计算结果可用来模拟激光等离子体的超热电子能谱和产额。     

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.     

Plane wave born cross sections including exchange forK-shell ionization of light atoms

Cross sections forK-shell ionization by electron impact have been calculated in plane wave Born approximation (PWBA) including outer screening with allowance for electron exchange in Ochkur approximation. The results agree reasonably with available experimental data.     

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.     

MEASUREMENT OF L-SHELL IONIZATION CROSS SECTIONS FOR NIOBIUM BY ELECTRON IMPACT

L-shell ionization cross sections of Nb by electron impact in the energy range from 3 to 40 keV have been determined with a Si(Li) X-ray detector. Influence of reflected electrons from backing on the measurement was corrected using an electron transport model. The experimental results are compared with theoretical calculations of Gryzinski and McGuire.