类氦离子的电子碰撞电离微分截面

本文主要利用扭曲波玻恩交换近似方法(DBE)计算类氦离子在电子碰撞下,相应不同的末态电子能量分配的电离截面(能量微分截面)。发现对这些微分截面在不同靶电荷及入射能量下,都可用带两个参数的高斯函数αexp(β(x—0.5)²)很好地拟合。还给出两个拟合参数随靶电荷和入射能量的变化曲线,以及讨论了在库仑波玻恩交换近似(CBE)和DBE两种不同近似下所得参数值的差别。计算结果也表阴,在低靶电荷和低入射能量时用DBE计算的必要性。 关键词：     

Al的能量吸收边缘和电子粒子数布居分析

给出了Al电子能量损失谱吸收边缘的理论解释、电子粒子数布居分析及不同散射分截面计算结果的比较.能量吸收边缘被归一化为每原子每电子伏的散射截面.对散射截面的贡献来自三个方面.第一是来自应用推广的Hückel带模型得到的电子从内层向价层的跃迁;第二是来自利用电子气模型得到的电离末态;第三是来自激发原子附近的原子产生的外行平面波弹性反向散射.理论计算结果与实验得到的电子能量损失谱符合较好. 关键词：     

Heavy fragment production cross sections from 1.05 GeV/nucleon 56Fe in C, Al, Cu, Pb, and CH2 targets

We have obtained charge-changing cross sections and partial cross sections for fragmentation of 1.05 GeV/nucleon Fe projectiles incident on H, C, Al, Cu, and Pb nuclei. The energy region covered by this experiment is critical for an understanding of galactic cosmic ray propagation and space radiation biophysics. Surviving primary beam particles and fragments with charges from 12 to 25 produced within a forward cone of half-angle 61 mrad were detected using a silicon detector telescope to identify their charge and the cross sections were calculated after correction of the measured yields for finite target thickness effects. The cross sections are compared to model calculations and to previous measurements. Cross sections for the production of fragments with even-numbered nuclear charges are seen to be enhanced in almost all cases.     

Photoemission cross section:A critical parameter in the impurity photovoltaic effect

A numerical study has been conducted to explore the role of photoemission cross sections in the impurity photovoltaic(IPV) effect for silicon solar cells doped with indium. The photovoltaic parameters(short-circuit current density, opencircuit voltage, and conversion efficiency) of the IPV solar cell were calculated as functions of variable electron and hole photoemission cross sections. The presented results show that the electron and hole photoemission cross sections play critical roles in the IPV effect. When the electron photoemission cross section is 10-20cm~2, the conversion efficiencyη of the IPV cell always has a negative gain(?η 0) if the IPV impurity is introduced. A large hole photoemission cross section can adversely impact IPV solar cell performance. The combination of a small hole photoemission cross section and a large electron photoemission cross section can achieve higher conversion efficiency for the IPV solar cell since a large electron photoemission cross section can enhance the necessary electron transition from the impurity level to the conduction band and a small hole photoemission cross section can reduce the needless sub-bandgap absorption. It is concluded that those impurities with small(large) hole photoemission cross section and large(small) electron photoemission cross section,whose energy levels are near the valence(or conduction) band edge, may be suitable for use in IPV solar cells. These results may help in judging whether or not an impurity is appropriate for use in IPV solar cells according to its electron and hole photoemission cross sections.     

Polarized inelastic electromagnetic processes in crystals with allowance for a new real distribution of nucleus charges and atomic electrons

The process of polarized electron-positron pair photoproduction via a polarized γ quantum in a crystalline medium is investigated using a new method that considers the distribution of nucleus charges and atomic electrons. Real changes in the cross sections of both polarized and nonpolarized electron pair production, and in the degrees of particle polarization in silicon crystal, are obtained.     

The feasibility of using neural networks to obtain cross sectionsfrom electron swarm data

The use of an artificial neural network as an optimization technique for treating the inverse problem of obtaining electron collision cross section from electron transport data is explored in which electron-impact cross sections from measured drift velocities, characteristic energies, and other swarm data are obtained. Momentum transfer cross sections obtained for a model problem and for xenon using a neural network are presented     

蓝宝石的近边精细结构和电子数布居分析

利用透射电子显微镜的电子能量损失谱研究了蓝宝石AlL和OK近边精细结构，给出了Al原子和O原子的电子数布居分析及不同分截面的比较.通过考虑一个原子在均匀固体中的电离来解释近边电离区中的元素效应.应用推广的Hückel分子轨道理论及反映了晶体变换对称性影响的布洛赫定理来计算电子从内层向价层的跃迁，从而解释了近边区域的化学效应.还考虑了附加的化学效应，这来自激发原子附近的原子产生的外行平面波弹性后向散射，由此产生电离区中的所谓延展精细结构.理论计算结果与实验得到的蓝宝石单相区电子能量损失谱符合较好. 关键词：     

高电荷态Ar^q＋与Ne碰撞中入射离子电荷交换截面的研究

报道Ar^q Ne(q=8，9，11，12)碰撞体系中多电子转移过程，得到了多组实验测量电荷交换截面数据，讨论入射离子电荷交换截面、反冲离子产生截面与入射离子电荷态、能量以及散射离子电荷态的关系，并且将实验结果与Ar^q Ar碰撞体系进行对比研究。在修正分子库仑过垒模型的基础上，对实验现象做了合理的解释。     

On the instability of ionospheric plasma originated by charge separations in the troposphere. The «UFO» phenomenon mechanism

Summary The troposphere is the seat of powerful processes which originate separation of electric charges. Thunder clouds give rise to a huge vertical separation of charges. But also known is a different electrification mechanism activated by wind, which allows for horizontal separation of charges. In favourable conditions, when charges are displaced at long distances, image charges appear in the ionspheric plasma and an upward electric field is originated which makes the ionosphere boundary unstable. If this occurs, recombination of displaced charges involves ionosphere conductivity and gives rise to a downward electron stream ejected from the bottom of the ionosphere. It may produce a peculiar airglow phenomenon, which consists of the emission of light in a narrow region lying at stratospheric or mesospheric altitudes. This outcome of the electrification process just mentioned shows a close connection with a special class of ?UFO? sightings, that is, those referred to by J. Hynek as ?nocturnal light? and which consist of bright specks of light moving in the night sky.     

V^20＋电子碰撞激发截面

采用ＣｏｕｌｏｍｂＢｏｒｎ交换近似，在修改了有效核电荷的Ｚ标度类氢模型下，计算了‘水窗’波段Ｖ２０＋离子精细结构能级间的电子碰撞激发截面     

Ionization of Hydrogen and Helium Atoms in Collisions with Relativistic Structural Heavy Ions

Based on the eikonal approximation, cross sections for single and double ionization of hydrogen and helium atoms in collisions with structural multiply charged heavy ions moving with relativistic velocities are calculated. In the present paper, the structural ions are taken to mean the ions with partially filled electronic shells. It is demonstrated that a consideration of the ion charge extension may noticeably change the corresponding cross sections compared to the cross sections for ionization by point ions having the same charges and energies.     

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     

Projectile fragmentation of silicon ions at 490 A MeV

Fragmentation cross sections are essential input parameters for propagation calculations which describe the effect of shielding against cosmic ray heavy nuclei by the walls of spacecraft or planetary habitat. Cross sections for the breakup of different elements are needed for different types of target material and for a wide range of energy.

For this purpose, we have extended our studies of projectile fragmentation. By using stacks containing CR-39 track detectors and targets ranging from CH₂ to Pb we have measured total and elemental fragmentation cross sections for fragments with charges Z_F>5, for silicon projectiles with energies of 490 AMeV. These new data sets allow us to improve our knowledge about the target and energy dependence of fragmentation cross sections.     

Electron excitation of hydrogen atom by ions impact in the energy range 20–1000 keV/amu

We have calculated the electron excitation cross sections of hydrogen atom by the impact of protons, alpha particles and He⁺ ions using the boundary corrected continuum intermediate state approximation in the intermediate and high energies. The calculated results are compared with other theoretical and experimental results. The angular influence of excitation to the H atom at the intermediate energy is also discussed. The distortion effects due to the projectile charges in reactions of electron excitation to bound states of the target H atom are shown in the intermediate and high collision energy.     

介质阻挡放电中两种亮暗点菱形斑图的光谱研究

空气和氩气混合气体的双水电极介质阻挡放电装置中,在电压升高过程中首次发现了两种由亮点和暗点组成的亮暗点菱形斑图。通过观察斑图照片可以发现： 第一种菱形斑图(菱形斑图Ⅰ)中的暗点处于由亮点组成的菱形单元的中心;第二种菱形斑图(菱形斑图Ⅱ)中的暗点恰好处于周围其他三个亮点的中心位置。利用发射光谱法,通过采集氮分子(N₂)第二正带系(C3Π_u→B3Π_g)发射谱线和氩原子696.54 nm(2P₂→1S₅)谱线的展宽,研究了两种菱形斑图中亮点和暗点的分子振动温度和电子密度。实验发现： 两种菱形斑图中暗点的分子振动温度均高于亮点,相对菱形斑图Ⅰ来说,菱形斑图Ⅱ中的亮点和暗点的分子振动温度均升高;而菱形斑图Ⅰ中暗点的电子密度低于亮点,菱形斑图Ⅱ中亮点和暗点的电子密度却几乎相等。两种菱形斑图中电子密度表现出不同的变化趋势,且在菱形斑图Ⅱ中表现出的规律尤为特殊,因而采用高速录像机对菱形斑图Ⅱ进行短曝光拍摄观察斑图中亮点和暗点的成分,发现暗点是体放电和沿面放电共存的状态。进一步研究从菱形斑图Ⅰ到菱形斑图Ⅱ的演化过程中三种斑图中亮点的电子密度,结果发现： 演化中间过程的斑图中的亮点的电子密度最大,菱形斑图Ⅱ中亮点的电子密度最低。实验结果对于研究斑图的自组织形成过程具有参考作用。     

中高能电子被O2及CF4分子散射的微分截面、弹性积分截面及动量转移截面

利用可加性规则，使用Roothaan-Hartree-Fock波函数，采用由束缚原子概念修正过的复光 学势，在300—1000eV内若干个能量点处计算了电子被O₂及CF₄分子 散射的微分截面、 弹性积分截面及动量转移截面，并将计算结果与实验结果及其他理论计算结果进行了比较. 比较的结果表明，利用被束缚原子概念修正过的复光学势及可加性规则进行计算，所得微分 散射截面的精度要比利用未修正的复光学势及可加性规则进行计算得到的结果准确得多；同 时，计算得到的弹性积分截面及动量转移截面也比较接近实验值.因此，在复光学势中采用 束缚原子概念可提高电子被分子散射的微分截面、弹性积分截面及动量转移截面的计算准确 度. 关键词： 电子散射 可加性规则 微分截面 弹性积分截面     

中高能电子和N_2（~1∑_g~＋）、CO（~1∑~＋）弹性散射全截面的计算

此文采用由原子轨道线性组合构成的自洽场分子轨道（ＳＣＦ－ＬＣＡＯ－ＭＯ），用一级玻恩近似（ＦＢＡ）计算了能量为１００－５０００ｅＶ的电子与弹性散射的微分截面和全截面。由于采用了Ｇａｕｓｓ函数的线性组合拟合Ｓｌａｔｅｒ函数的方法（ＳＴＯ－ＫＧ），得到了弹性散射微分截面的解析表达式，使计算大大简化。计算得到的电子和Ｎ２，ＣＯ散射的总截面和实验结果进行了比较，当入射电子的能量大于１ｋｅＶ时，理论值和实验值之间符合得很好。     

Interaction between multiple spatial solitons in the diffraction catastrophe region upon focusing a high-power laser beam in a nonlinear medium

When a high-power laser beam is focused in a nonlinear Kerr medium, beam self-diffraction by induced inhomogeneities of the refractive index is observed. A method for calculating the field amplitude and phase in the focal region with regard for self-diffraction by self-induced inhomogeneities is developed. Computer analysis of saturable Kerr media showed that the optical-field region with the least cross section of the focal pattern is followed by that of chaotically radiating “splashes” and long filaments. The latter radiate outward from the region of the caustic waist over long distances. They represent bright spatial solitons, which channel a significant portion of the primary beam energy. No less than 8–12 clear-cut solitons traveling in the positive z direction and moving apart in the transverse (x, y) plane are observed in the cross section. The field amplitude oscillates along each of the solitons. Various parameters of the saturable Kerr medium are taken into account.     

The time dependent solution of the masterequation for a laser system

Calculations of the cross sections for collision-induced transitions between Zeeman sublevels of excited alcali atoms are proposed, which are independent from dynamical models. 1. Supposing that the spin of the valence electron does not flip, the transition matrix, describing collision-induced deorientation of the orbital angular momentum, is analysed considering invariance principles only. Consequently the cross sections for depolarizing collisions are given by two dynamical parameters. 2. The full transition matrix, describing deorientation of the orbital angular momentum as well as of the spin of the valence electron, is analysed in the same way. In this general case the depolarizing cross sections are given by six dynamical parameters.     

中高能电子被氟代甲烷散射的总截面计算

利用可加性规则,使用Hartree-Fock 波函数,采用被束缚原子概念修正过的复光学势,首次在100～5 000eV内对电子被具有较多电子数的氟代甲烷分子散射的总截面进行了计算,且将计算值与实验值及经验公式进行了比较,得出了被束缚原子概念修正过的复光学势可成功用于"电子-氟代甲烷"散射总截面计算的结论;研究了"电子-氟代甲烷"的散射总截面与目标分子总电子数及电子入射能量间的关系,初步分析了结构因子与总电荷数相关的原因,并指出了对复光学势进行进一步修正时应遵循的原则.