共查询到18条相似文献,搜索用时 203 毫秒
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在玻恩近似下,建立了高能电子与原子、离于非弹性碰撞过程的相对论性理论计算方法,并以类Li等电子系列为例,阐明了电子与原子、离子非弹性碰撞过程的相对论效应.它包括:1.靶原子的相对论效应,它随原子序数的增加而增大.低z靶(如Li)的相对论效应可以忽略;对Au~(+76)靶的2_3—3p跃迁,广义振子强度相对论性计算值比相应的非相对论性值小27.1%.2.入射电子的相对论效应,它随入射电子能量的增加而增大.对高能入射电子,在特殊角度,要考虑广义振子强度横场项对微分截面的影响.在极端相对论情况下,如入射电子动能
关键词: 相似文献
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快电子与原子分子碰撞实验 总被引:1,自引:0,他引:1
仅由原子分子体系本身的物理量决定.1935年,Bethe证明广义振子强度与光学振子强度之间有如下关系:f(Ej,q)=f0(Ej)+Aq2+Bq4+…,df(E,q)/dE=df0(E)/dE+Aq2+Bq4+…当q→0即高入射电子能量(T>>E)和0°散射角情况下,不管玻恩近似是否成立,都有:方程右边各物理量实验上都能测量.于是用快电子碰撞测量0°散射微分截面,即通过能量损失谱测量可得光学振子强度. 相似文献
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利用相对论扭曲波方法和新发展的研究电子碰撞激发过程的计算程序REIE06,系统计算了电子碰撞激发高离化态类镍Gd36+和Rn58+—U64+(Z=86—92)离子从基态到4l(l=s,p,d,f)次壳层精细结构能级的碰撞强度和截面.研究了随等电子系列变化时,从基态到与X射线激光有关的3d94p和3d94d激发态能级的电子碰撞激发截面随Z的变化,讨论了强的组态相互作用对高离化态类镍离子截面的影响.通过对Gd36+离子涉及X射线激光跃迁的相关能级电子碰撞激发速率系数的计算,分析了等离子体中电子温度对碰撞过程的影响.同时,目前部分计算结果与以往的理论结果进行了比较,得到了很好的一致性.
关键词:
电子碰撞激发
相对论扭曲波方法
高离化态类镍离子 相似文献
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利用初态程函近似的连续扭曲波方法研究了He2+离子与H原子的碰撞电离过程. 计 算得到了入射离子能量从30keV/u到2000keV/u的碰撞电离总截面、随电离电子能量和角度变 化的一阶和二阶微分散射截面,及随入射离子能量变化的电离电子平均能量.计算的总电离 截面与其他理论和实验结果进行了比较,在入射离子能量大于100keV/u的能区,计算结果 与实验符合得很好;在较低的能区,各种理论结果之间有较大差别,计算结果比实验约小50 %.利用计算的二阶微分散射截面讨论了软碰撞、电子俘获到入射离子连续态、两体相遇碰 撞等碰撞电离机理.
关键词:
重粒子碰撞电离
初态程函近似
总截面
一阶和二阶微分散射截面 相似文献
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基于低能离子与原子碰撞的分子库仑过垒模型,简要描述了与入射离子速度相关的反应窗理论.根据这一理论,计算了不同碰撞速度时O8+-H,Ar8+-H,Ar8+-He,Ne10+-He及Ar18+-He等碰撞体系单电子俘获过程的微分截面,还计算了碰撞速度为0.53 a.u.时15N7+-Ne碰撞体系单电子、双电子及三电子俘获过程的微分截面,并与他人的实验结果作了比较.研究发现,反应窗理论预言的末态电子分布与实验结果符合较好.理论和实验研究表明,随着碰撞速度的增加反应窗变宽;反应窗理论所预言的微分截面,当Q值较小时比实验结果偏大,当Q值较大时比实验结果偏小.
关键词:
反应窗理论
态选择微分截面
分子库仑过垒模型
离子与原子碰撞 相似文献
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Ph. V. Demekhin I. D. Petrov B. M. Lagutin V. L. Sukhorukov A. Neogi P. Yeates E. T. Kennedy M. W. D. Mansfield J. T. Costello 《Optics and Spectroscopy》2007,102(2):149-158
The photoionization cross sections for the 4p shell of ions of the Kr isoelectronic sequence Rb+, Sr2+, and Y3+ are calculated. The configuration interaction theory and the perturbation theory are used to describe the many-electron effects. The relativistic effects are taken into account in the Pauli-Fock approximation. The calculated resonance structure of photoionization cross sections for the 4p shell in the region below the 4s threshold associated with the autoionization of the 4s-np singly excited states and the 4p4p-nln′l′ doubly excited states reproduces the results of recent measurements of total photoabsorption cross sections for the Rb+, Sr2+, and Y3+ ions. It is found that, as the nuclear charge in the isoelectronic sequence increases, the ratio between the direct and correlation parts of amplitudes of the 4s-(n/?)p transition changes and, as the consequence, the minimum of the photoionization cross section of the 4s shell shifts from the continuous spectrum to the region of states of discrete spectrum. This accounts for the strong changes in the shape of the 4s-np resonances in the photoionization cross sections for the 4p shell of Rb+, Sr2+, and Y3+, as well as the distinction between the shapes of the 4s-6p 1/2 mirror resonance in the partial 4p 1/2 and 4p 3/2 photoionization cross sections for the Y3+ ion which do not suppress each other in the total photoionization cross section, as is the case for similar resonances in Rb+ and Sr2+. 相似文献
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G. Kroner A. Hofmann G. Philipp K. Thomas 《Zeitschrift für Physik A Hadrons and Nuclei》1971,242(4):308-319
For the reaction40Ca(d,α)38K differential cross sections for the excitation of the low lying states in38K have been measured at bombarding energies between 5 and 10 MeV. Total cross sections have been calculated using the statistical theory. It was found, that in the whole energy region the isotropic background of the angular distributions gives a good estimation of the compound contribution to the reaction cross section. 相似文献
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Heloisa Maria Boechat-Roberty Elmar O. Uhl Flavio N. Rodrigues Maria Cristina A. Lopes Maria Luiza M. Rocco Carlos A. Lucas Alexandre B. Rocha Carlos E. Bielschowsky Gerardo Gerson B. de Souza 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2013,67(2):1-6
Electron energy-loss spectra for the butadiene molecule were measured in the scattering angular range of 2.0° to 8.0°, in an energy-loss range from 2 to 50 eV, using 1000 eV incident electrons. The absolute generalized oscillator strength (GOS) and inelastic cross section have been determined for the \hbox{$\tilde{\rm X}^{1}$}?X1A g → 11B u transition. The absolute elastic differential cross section was also determined spanning an angular range from 2.0° to 40.0°. From a small angle electron energy-loss spectrum, the optical oscillator distribution (photoabsorption spectrum) for the butadiene molecule was obtained in the 2 to 100 eV photon energy range. Accurate ab initio calculations have been performed, within the First Born Approximation, for generalized oscillator strength (GOS) and excitation energies for the \hbox{$\tilde{\rm X}^{1}$}?X1A g → 11B u and \hbox{$\tilde{\rm X}^{1}$}?X1A g → 21A g transitions. Our results emphasize the importance of using highly correlated wavefunctions and accurate methodologies in the calculation of the GOS for electron impact-induced electronic transitions in molecules. 相似文献
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V. A. Zilitis 《Optics and Spectroscopy》2009,107(1):54-57
A simple formula that allows the determination of the oscillator strengths for all transitions of principal series of the Rb-like ions is obtained from the relationship between the oscillator strengths and the corresponding photoionization cross sections. The photoionization cross sections are calculated by the Dirac-Fock method with allowance for the retardation and approximated by an analytic formula. The data for ten ions of the rubidium isoelectronic sequence (from Sr+ to Ag10+) are presented. Two types of gauges corresponding to the transition operators in length and velocity forms are considered. 相似文献
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Shu-Xing Wang 《中国物理 B》2022,31(8):83401-083401
Electron-impact excitation integral cross sections play an important role in understanding the energy transfer processes in many applied physics. Practical applications require integral cross sections in a wide collision energy range from the excitation threshold to several keV. The recently developed BE-scaling method is able to meet the demands of integral cross sections for dipole-allowed transitions while the prerequisite relies on the accurate generalized oscillator strengths. Fast electron and x-ray scatterings are the conventional experimental techniques to approach the generalized oscillator strengths, and the joint study by both methods can provide credible cross-checks. The validated generalized oscillator strengths can then be used to extrapolate optical oscillator strengths by fitting the data with the Lassettre formula. The fitted curve also enables the integration of generalized oscillator strengths over the whole momentum transfer region to obtain the BE-scaled integral excitation cross sections. Here, experimental measurements by both fast electron and x-ray scattering of argon and carbon dioxide are reviewed. The integral cross sections for some low-lying states are derived from the cross-checked generalized oscillator strengths for the first time. The integral cross sections presented in this paper are openly available at https://doi.org/10.11922/sciencedb.01466. 相似文献
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利用基于多组态Dirac-Hartree-Fock(MCDHF) 理论方法的相对论原子结构计算程序包GRASP2K, 细致计算了中性锂原子、类锂Be+, C3+, O5+, Ne7+, Ar15+, Fe23+, Mo39+, W71+及U89 + 离子基组态及较低的激发组态1s2nl (n = 2---4, l =s,p,d,f) 的精细结构能级, 以及各能级间发生电偶极(E1) 自发辐射跃迁的能量、概率及振子强度. 同时, 在非相对论极限下, 计算了其相关原子参数. 通过对相对论及非相对论计算结果的比较, 系统研究了相对论效应对类锂等电子系列离子能级结构及E1跃迁性质的影响, 揭示了随原子核电荷数Z变化时, 跃迁能、振子强度强烈依赖于量子数n, l, j变化的规律; 同时, 目前的计算结果与其他已有的理论计算及实验测量结果进行了比较. 相似文献
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For a series of parameter values characterizing an axially symmetric nuclear orientation, the differential cross sections of electrical excitation of oriented7Li,10B nuclei by completely polarized ultrarelativistic electrons with nuclear transition to the first excited states are calculated as a function of the transmitted momentum q. The nucleus is described by a multiparticle oscillator shell model in intermediate coupling. The contribution to the cross section due to nuclear polarization is calculated; it is compared with the influence of the alignment of the nuclei. It is shown that the cross sections calculated for these two cases may differ significantly, both in magnitude and in the character of the dependence on q. For a series of transitions to low-lying levels of the7Li,10B nuclei, systems of equations in terms of reduced nuclear matrix elements of multipole transitions and statistical solutions are obtained; their solution, with cross sections measured in different kinematic conditions but for fixed q as parameters, allows not only the absolute values of the desired quantities to be established, but also the relative phases of the reduced matrix elements.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 84–88, May, 1990. 相似文献
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J. Geiger 《Zeitschrift für Physik A Hadrons and Nuclei》1963,175(5):530-542
The theoretical differential cross section for the elastic scattering and for the excitation of optical transitions in helium by electron impact has been refined in Born approximation by use of the two parameter Eckart eigenfunction for the ground state and for the excited states. The angular distributions of 25 kev electrons scattered elastically and inelastically by helium were measured in the angular range 2·3·10?4≦?≦4·10?2. The intensity distribution of the elastically scattered electrons is in accordance with the theoretical curve for?>7·10?3 and is disturbed at smaller angles by the primary beam. Normalization of the experimental values to the theoretical elastic differential cross section leads to agreement between the experimental differential cross section for the excitation of the 21 P and 31 P state and the scattering formulae given in this paper. There are small systematic deviations (<20%) for the 21 P differential cross section in the angular range 3·10?3<?<1·10?2 only. The oscillator strength of these two transitions has been determined from the scattering measurements:f 21=0·312±0·04 andf 31=0·0898±0·006. 相似文献