Electron Traps with a Wide Range of Capture Cross Sections in Powdery ZnS-Based Luminophors

Using the method of thermally stimulated luminescence, the phenomenon of spatial modulation of the capture cross section (S_t) of electron traps with a level of E_c − 0.18 eV in powdery luminophors Zn_0.97Cd_0.03S 〈Cu, Cl〉 with green luminescence and ZnS〈Ag, Cl〉 with blue luminescence by a collective electric field of macroinhomogeneity has been investigated. The maximum value of the effect (width of the range of values of S_t) attains five orders of magnitude, with the size of the powder grains being of order 1 µm. A model is suggested, according to which traps with E_c − 0.18 eV with an extended range of values of S_t represent an isolated anionic vacancy in a region of the collective field of macroscopic inhomogeneity that is the negatively charged surface of the powder grains. The extension of the range of values of S_t is the result of modulation of the kinetic parameters of electron traps E_c − 0.18 eV depending on the spatial position occupied by the anionic vacancy relative to the surface of the powder grains.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 2, pp. 202–206, March–April, 2005.     

1.0 MeV电子碰撞引起Ta 和Au 内壳电离截面的测量

无论对深入理解电子-原子的作用机制,还是在材料等领域的实际应用,电子轰击原子的内壳电离截面都具有重要意义。当前电子碰撞引起原子内壳电离的实验数据多集中在几十keV 入射能量和中小Z 靶原子,其它数据相对比较缺乏。本工作以能量为1.0 MeV电子轰击Ta 和Au 靶,通过测量靶原子特征X射线的产额,获得其K壳电离截面分别为13.3 和10.1 b,L 壳电离截面分别为554 和338 b。并将实验结果和相应的理论进行了对比,结果显示,本实验测得的K壳电离截面与Casnati、Hombourger 理论值、L 壳电离截面与Scoeld和Born-Bethe 的理论值相符。Accurate experimental data for atomic inner-shell ionization cross-sections by electrons are of basic importance both in understanding inelastic electron-atom interaction and its application. Up to now, most of available data on this process were mainly concentrated on the low and medium Z atoms by the bombardment of low energy electrons. In present experiments K-shell and L-shell ionization cross-sections of Ta and Au in collisions with 1.0 MeV eleltron were determined by measuring the characteristic X-rays emitted from the target atoms. For the present collision systems the K-shell ionization cross-sections were found to be 13.3 and 10.1 b,and the L-shell ionization cross sections were 554 and 338 b, respectively. The measured K-shell ionization cross sections are in reasonable agreement with the theoretic predictions of Casnati and Hombourger, while L-shell ionization cross sections are consistent with the theoretical results of Soc eld and Born-Bethey.     

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.     

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.     

Probing proton halo of the exotic nucleus28S by elastic electron scattering

Elastic electron scattering on the exotic light nucleus²⁸S is investigated in the plane wave Born approximation. The variation of the squared form factors of²⁸S with momentum transfer is compared with that of³²S. It is found that the behavior of the form factors near the second minimum (with a moderate momentum transfer) is sensitive to the alteration of the charge density distribution of halo protons in²⁸S. This indicates that elastic electron scattering can be a good probe of the structure of proton-halo nuclei.     

Electron excitation processes in low energy collisions of hydrogen-helium atoms

The electron excitation processes of $rm H(1s) + He(1s^{2}) to H(2s/2p) + He(1s^{2})$ are studied in impact energy range of 20—2000 eV/u by using the quantum-mechanical molecular orbital close-coupling (QMOCC) method. Total and state-selective cross sections have been obtained and compared with the available theoretical and experimental results. The results agree well with available measurements in the overlapping energy regions overall. The comparison of our results with other theoretical calculations further demonstrates the importance of considering a sufficient number of channels. The datasets presented in this paper, including the excitation cross sections, are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00083.     

Electron impact ionisation cross section for organoplatinum compounds

This article reports electron impact ionisation cross sections for platinum-based drugs viz., cisplatin (H₆N₂Cl₂Pt), carboplatin (C₆H₁₂N₂O₄Pt), oxaliplatin (C₈H₁₄N₂O₄Pt), nedaplatin (C₂H₈N₂O₃Pt) and satraplatin (C₁₀H₂₂ClN₂O₄Pt) complexes used in the cancer chemotherapy. The multi-scattering centre spherical complex optical potential formalism is used to obtain the inelastic cross section for these large molecules upon electron impact. The ionisation cross section is derived from the inelastic cross section employing complex scattering potential–ionisation contribution method. Comparison is made with previous results, where ever available and overall a reasonable agreement is observed. This is the first attempt to report total ionisation cross sections for nedaplatin and satraplatin complexes.     

甲硫醇的低能电子弹性碰撞截面

使用R-matrix方法在静态交换和静态交换加极化两种模型下研究电子-甲硫醇的弹性散射．计算的弹性散射截面与已有的实验结果符合的很好．静态交换极化模型探测到了两个具有2A'对称性的形 状共振态,能量位置分别在4.06和8.32 eV．通过波恩修正,用更高的分波l>4获得了收敛的截面．还使用计算的动量转移截面数据计算了200～30000 K的高效电子碰撞频率.     

Probing proton halo of the exotic nucleus ~(28)S by elastic electron scattering

~~Probing proton halo of the exotic nucleus ~(28)S by elastic electron scattering~~     

慢电子与氧原子之间相互作用--光分解和散射的研究

利用R-矩阵方法进行了慢电子与氧原子之间相互作用的密耦计算.给出了光子能量从阈值到7eV范围内的氧负离子的光分解总截面,各个对称性分截面以及主要电离通道对分截面的贡献.并和已知的实验结果和理论计算结果进行了对比.同时计算了慢电子与氧原子弹性碰撞散射截面,并与试验结果和理论结果进行了分析比较.     

低能He2+-He反应中单电子俘获微分散射过程的实验研究

利用冷靶反冲离子动量谱仪装置系统研究了20—40 keV He²⁺-He碰撞体系的态选择单电子俘获过程,实验获得了单电子俘获过程的态选择截面以及角微分截面.在所研究的能区范围,电子俘获到L壳层的截面最大,为主要的反应道,这与分子库仑过垒模型的反应窗理论的预测一致.实验测量的态选择截面与原子轨道紧耦合的计算结果很好地符合,与光谱方法的测量结果存在一定的差别,主要原因是光谱方法不能测量完整的反应通道信息.实验结果表明,总角微分截面在小角度范围主要来源于电子俘获到基态的贡献,在大角度范围主要来自电子俘获到激发态的贡献;电子俘获到基态的和激发态的角微分截面均出现振荡结构,这种振荡来源于电子俘获反应中分子轨道之间的相干效应.实验测量的角微分截面与其他实验和紧耦合方法的计算结果进行了比较和分析. 关键词： 冷靶反冲离子动量谱仪 态选择电子俘获 态选择截面 角微分截面     

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。     

Electron wind effect in semiconducting cobalt oxide

Abstract

The coupling between ionic and electronic motion in p-type semiconducting cobalt oxide is studied with the help of radioactive tracers moving in an applied electrical field. First results show that the cross effect cannot be neglected, resulting in an apparent charge z _Co=1.6 for the cobalt ions.     

Differential, elastic integral and moment transfer cross sections for electron scattering from N2 at intermediate- and high-energies

A complex optical model potential modified by incorporating the concept of bonded atom, with the overlapping effect of electron clouds between two atoms in a molecule taken into consideration, is firstly employed to calculate the differential cross sections, elastic integral cross sections, and moment transfer cross sections for electron scattering from molecular nitrogen over the energy range 300—1000eV by using additivity rule model at Hartree—Fock level. The bonded-atom concept is used in the study of the complex optical model potential composed of static, exchange, correlation polarization and absorption contributions. The calculated quantitative molecular differential cross sections, elastic integral cross sections, and moment transfer cross sections are compared with the experimental and theoretical ones wherever available, and they are found to be in good agreement with each other. It is shown that the additivity rule model together with the complex optical model potential modified by incorporating the concept of bonded atom is completely suitable for the calculations of differential cross section, elastic integral cross section and moment transfer cross section over the intermediate- and high-energy ranges.     

Fractional-charge and fractional-spin errors in range-separated density-functional theory

ABSTRACT

We investigate fractional-charge and fractional-spin errors in range-separated density-functional theory (DFT). Specifically, we consider the range-separated hybrid (RSH) method which combines long-range Hartree-Fock (HF) exchange with a short-range semilocal exchange-correlation density functional, and the RSH+MP2 method which adds long-range, second-order Møller-Plesset (MP2) correlation. Results on atoms and molecules show that the fractional-charge errors obtained in RSH are much smaller than in the standard Kohn-Sham (KS) scheme applied with semilocal or hybrid approximations, and also generally smaller than in the standard HF method. The RSH+MP2 method tends to have smaller fractional-charge errors than standard MP2 for the most diffuse systems, but larger fractional-charge errors for the more compact systems. Even though the individual contributions to the fractional-spin errors in the H atom coming from the short-range exchange and correlation density-functional approximations are smaller than the corresponding contributions for the full-range exchange and correlation density-functional approximations, RSH gives fractional-spin errors that are larger than in the standard KS scheme and only slightly smaller than in standard HF. Adding long-range MP2 correlation only leads to infinite fractional-spin errors. This work clarifies the successes and limitations of range-separated DFT approaches for eliminating self-interaction and static-correlation errors.     

中高能28Si碎裂截面研究进展

介绍了利用CR-39探测器对28Si与不同靶作用的电荷变化总截面和分截面的研究进展,给出723AMeV 28Si与碳靶作用电荷变化总截面和分截面的最新实验结果。对28Si与靶核反应电荷变化总截面和分截面与束流能量和靶核质量的关系进行了讨论,发现束流能量大于200 AMeV时,中高能28Si与不同靶核反应电荷变化总截面与束流能量无关,分截面表现出明显的奇偶效应,且随靶核质量数的增加而增加。In this paper, the development of the total and partial charge changing cross sections of 28Si ions beam in different targets using the CR-39 detectors are reviewed. The newest experimental results of the total and partial charge changing cross sections of 28Si in carbon target at 723 AMeV are presented. The dependence of the target mass and the cross sections of 28Si including the total and the partial charge changing cross sections are discussed. It is found that the total charge changing cross sections of 28Si are independent of the energy when the energy of the ions beam is greater than 200 AMeV. The partial charge changing cross sections show an obviously odd-even effect, and increase with the increasing of the mass number of the target.     

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。     

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.     

Absolute differential, elastic integrated and moment transfer cross sections for electron--OCS collisions at intermediate and high energies

A complex optical model potential modified by incorporating the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between atoms in a molecule, is firstly employed to calculate the absolute differential, elastic integrated and moment transfer cross sections for electron scattering by OCS over the incident energy range from 200 to 1000\,eV using the additivity rule model at Hartree--Fock level. The calculated results are compared with those obtained by experiment and other theories wherever available, and good agreement is obtained over a wide energy range. It is shown that the additivity rule model together with the modified potential is completely suitable for calculating the absolute differential, elastic integrated and moment transfer cross sections of electron scattering by molecules such as OCS.