Electron impact ionization rate coefficients and cross sections for highly ionized iron

Electron impact ionization cross sections for the ions Fe(XVII)-(XXVI) have been computed in a distorted wave exchange approximation. Analytic fits are provided for the cross section data, as well as for the rate coefficients assuming a Maxwellian electron velocity distribution. For ejection of a 2p ground state electron, the scaled ionization rate was found to depend linearly on the number of 2p electrons in the ion.     

Eine Koinzidenzmessung zum Elementarprozeß der Elektron-Elektron-Bremsstrahlung bei 300 keV

The absolute cross section of electron-electron bremsstrahlung which is differential in all the free kinematical variables was measured by using an electron-photon coincidence technique. An electron beam of 300 keV was used, incident on a carbon target. Within the experimental errors we found agreement with recent theoretical calculations. Simultaneously with the electron-electron bremsstrahlung the absolute cross section of electron-nucleus bremsstrahlung of carbon was measured.     

Double electron capture in H+ + Mg collisions

The cross section for double electron capture in H⁺ + Mg collisions has been measured over the proton energy range 1.1 keV to 80 keV. The cross section exhibits structure at low energies and is rising below 2.8 keV. Results are discussed and compared with recent multichannel Landau-Zener calculations and with previous measurements.     

一种考虑几何屏蔽效应的计算“电子-分子”散射总截面的可加性规则修正方法

在考虑分子内原子间的几何屏蔽效应随电子入射能量变化的基础上, 提出了一种能够在中、高能区准确计算“电子-分子”散射总截面的可加性规则修正方法. 利用这一修正后的可加性规则并使用“电子-C, H, O, N原子”散射总截面的实验数据, 在50—5000 eV内计算了电子被NO, N₂O, NO₂和C₂H₆分子散射的总截面, 且将计算结果与实验结果及其他理论结果进行了比较. 结果表明, 利用这一方法修正过的可加性规则进行计 关键词： 电子散射 可加性规则 总截面 几何屏蔽效应     

裸核离子与中性原子碰撞电离过程的理论研究

基于处理裸核离子与中性原子碰撞电离过程的OBKN和ECPSSR理论模型,系统计算了不同裸核离子与中性原子碰撞K壳层电子俘获截面和直接电离截面,并与其它文献已有的理论和实验结果进行了比较.研究结果表明：碰撞能量较低时,电子俘获截面大于直接电离截面,随着碰撞能量的增加,电子俘获截面和直接电离截面均是先增大后减小且直接电离截面减小地非常缓慢,高能时,直接电离截面大于电子俘获截面.当入射炮弹离子速度接近0.67倍靶原子K壳层电子速度时,电子俘获截面达到最大值,而当入射炮弹离子速度接近靶原子K壳层电子速度时,直接电离截面达到最大值.     

裸核离子与中性原子碰撞电离过程的理论研究

基于处理裸核离子与中性原子碰撞电离过程的OBKN和ECPSSR理论模型,系统计算了不同裸核离子与中性原子碰撞K壳层电子俘获截面和直接电离截面,并与其它文献已有的理论和实验结果进行了比较.研究结果表明:碰撞能量较低时,电子俘获截面大于直接电离截面,随着碰撞能量的增加,电子俘获截面和直接电离截面均是先增大后减小且直接电离截面减小地非常缓慢,高能时,直接电离截面大于电子俘获截面.当入射炮弹离子速度接近0.67倍靶原子K壳层电子速度时,电子俘获截面达到最大值,而当入射炮弹离子速度接近靶原子K壳层电子速度时,直接电离截面达到最大值.     

The photoneutron cross section in 13C

The photoneutron cross section in ¹³C was measured using bremsstrahlung from an electron synchrotron operated in energy sweeping mode. Neutrons were detected by a multi-BF₃-counter detection system. Decorrelated cross-section ordinates were calculated directly using a modified Leiss-Penfold analysis. The cross section from threshold to 25 MeV shows detailed structure, some nine maxima, in agreement with recent continuum shell-model calculations.     

Effect of the structure of the singly charged ion on the cross section for electron capture

The calculations of the cross section for single-electron capture by fast ions are carried out in the Oppenheimer-Brinkman-Kramers approximation. The dependences of the experimental and calculated cross sections for single-electron capture by fast singly charged ions on the collision energy coincide. This makes it possible to estimate the cross section for electron capture in the case of ion-atom collisions if experimental data are absent. The results of calculations for projectiles with filled s-type subshells show that the contribution of electron capture channels to the excited state of the scattered particle depends on the collision energy.     

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.     

Messung der Winkelverteilung und des Wirkungsquerschnittes beim Elementarprozeß der Elektron-Elektron-Bremsstrahlung

By using an electron-photon coincidence technique, we have measured the absolute cross section of electron-electron bremsstrahlung in dependence of the photon emission angle for a definite energy and a definite angle of the outgoing electron. An electron beam of 300 keV was used, incident on a carbon target. Within the experimental errors we find agreement with theoretical calculations. Simultaneously with the electron-electron bremsstrahlung the elementary process of electron-nucleus bremsstrahlung of carbon was measured.     

K-line X-ray fluorescence from highly charged iron ions under dense astrophysical plasma conditions

In the present work, we report an investigation of plasma environment effects on the atomic parameters associated with the K-vacancy states in highly charged iron ions within the astrophysical context of accretion disks around black holes. More particularly, the sensitivity of K-line X-ray fluorescence parameters (wavelengths, radiative transition probabilities, and Auger rates) in Fe XVII–Fe XXV ions has been estimated for plasma conditions characterized by an electron temperature ranging from 10⁵ to 10⁷ K and an electron density ranging from 10¹⁸ to 10²² cm⁻³. In order to do this, relativistic multiconfiguration Dirac-Fock atomic structure calculations have been carried out by considering a time averaged Debye-Hückel potential for both the electron–nucleus and electron–electron interactions.     

The angular distribution of the 3p electrons and the partial cross section of the 3s electrons of argon from threshold to 70 eV

The angular distribution parameter β has been measured for the argon 3p electrons in the energy range 0–70 eV above threshold using a synchrotron light source. The absolute photoionization cross section of argon 3s electrons has also been determined in the 0–60 eV region above threshold. Both sets of data are compared with recent theoretical calculations which include electron correlation effects.     

BeCl_2分子的低能电子弹性散射研究

基于R矩阵理论方法,通过构建BeCl_2分子的静态交换势模型(SE),静态交换加极化势模型(SEP)和密耦合模型(CC),在0-10 eV能量范围内首次研究了低能电子与BeCl_2分子的散射动力学过程,预测了弹性散射积分截面,并在三种模型中分别发现一个来自B_(2u)和B_(3u)对称性贡献的势形共振态.讨论了这些共振态随着极化效应的变化,获得了收敛的截面和共振态结果.进一步使用POLYDCS程序首次计算了电子与BeCl_2分子的散射微分截面(DCS)以及动量转移截面(MTCS).当前研究结果将为天体物理和等离子体物理提供重要的截面数据.     

Single electrons from heavy-flavor decays in collisions at

The invariant differential cross section for inclusive electron production in p+p collisions at [FORMULA: SEE TEXT] has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over the transverse momentum range 0.4相似文献   

Absolute cross-section measurements of inner-shell ionization

Cross section ratios for K- and L-shell ionization of thin silver and gold targets by positron and electron impact have been determined at projectile energies of 30–70 keV. The experimental results are confirmed by calculations in plane wave Born approximation (PWBA) which include an electron exchange term and account for the deceleration or acceleration of the incident projectile in the nuclear field of the target atom. We report first absolute cross sections for K- and L-shell ionization of silver and gold targets by lepton impact in the threshold region. We have measured the corresponding cross sections for electron (e^–) impact with an electron gun and the same experimental set-up.     

Atomic parameters for Fe(XV) and Ni(XVII)

Transition probabilities and collision strengths are tabulated, between the fourteen lowest levels of the magnesium-like ions Fe(XV) and Ni(XVII), for use in calculations of line intensities radiated from laboratory and astrophysical plasmas.     

Measurement of the absolute cross section for the elementary process of atomic field bremsstrahlung

Coincidence measurements of the absolute cross section for the production of bremsstrahlung by electrons in the field of gold atoms are reported. The incident electron energyT ₀ was 300 keV. Measurements were made for four different combinations of electron scattering angle and photon emission angle over a wide range of the relative photon energyk/T ₀ up tok/T ₀=0.83. The measured cross sections are compared with results of Bethe-Heitler and Elwert-Haug calculations     

Asymptotics of the cross section of the electron loss by fast ions in light media

The dependence of the single electron loss cross section on the nuclear charge Z of a projectile and on the nuclear charge Zt of a target atom for fast collisions is studied theoretically using the plane-wave Born approximation and the sum rule. The results of calculations for fast singly and triply charged ions show that the single electron loss cross section increases monotonically as Z and Zt increase. This can be used to interpolate cross sections of processes if there are no experimental data. The results of calculations compare with the experimental and theoretical data of other authors.     

Influence of resonances on spectral formation of x-ray lines in Fe XVII

New theoretical results from large-scale relativistic close coupling calculations reveal the precise effect of resonances in collisional excitation of x-ray lines of Ne-like Fe XVII. By employing the Breit-Pauli R-matrix method and an 89-level eigenfunction expansion, including up to n = 4 levels, significant resonance enhancement of the collision strengths of forbidden and intercombination transitions is shown. The present results should help resolve long-standing discrepancies; in particular, the present line ratios of three benchmark diagnostic lines 3C, 3D, and 3E at 15.014, 15.265, and 15.456 A, respectively, are in excellent agreement with two independent measurements on electron-beam ion traps. Strong energy dependence in cross sections due to resonances is demonstrated.     

Triple differential cross section for autoionisation of helium by electron impact at 100 eV

Cross sections for autoionisation of helium by electron impact have been measured by an electron-electron coincidence technique at an incident electron energy of 100 eV and a scattering angle of 15°. The variation of the direct ionisation cross section and the resonance parameters for the (2s2p)¹P autoionising level, as functions of ejected electron angle, are compared with the results of recent theoretical calculations.