共查询到19条相似文献,搜索用时 140 毫秒
1.
基于多组态Dirac-Fock方法的程序包GRASP92和RATIP及在此基础上最新发展的RELPHOTO08程序, 系统地研究了高离化态金离子M壳层的光电离截面随入射光子能量、 离化度以及壳层的变化规律。结果表明: 光电离截面随光子能量的增大而单调减小; 电离nl电子时, 如果相关电子的主量子数较大, 则该电子存在与否对其光电离截面几乎没有影响; 在同一离化度下, 角量子数l可引起两种性质不同的效应, 其相互竞争可导致光电离截面随入射光子能量的复杂变化。Based on multiconfiguration Dirac Fock method and the corresponding packages GRASP92 and RATIP, as well as the newly developed RELPHOTO08, the variations of M subshell photoionization cross sections with the photon energy, ionization degree and subshells for highly charged gold ions are studied systemically. The present results show that the cross sections are decreasing monotonously with the photon energy; for the photoionization of nl electrons, if the principal quantum number of removed electron is large enough, the cross sections are essentially unchanged upon the presence or absence of outer electrons; for same ionization degree, the angular quantum number introduces two opposite effects which could exist simultaneously, and the intricate variations of cross sections with the photon energy originate from the competition between these two different effects. 相似文献
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Interference effects on the photoionization cross sections between two neighbouring atoms: nitrogen as an example 下载免费PDF全文
Interference effects on the photoionization cross sections
between two neighbouring atoms are considered based on the coherent
scattering of the ionized electrons by the two nuclei when their
separation is less than or comparable to the de Broglie wave length
of the ionized electrons. As an example, the single atomic nitrogen
ionization cross section and the total cross sections of two
nitrogen atoms with coherently added photoionization amplitudes are
calculated from the threshold to about 60~\AA (1~\AA=0.1~nm) of the
photon energy. The photoionization cross sections of atomic nitrogen
are obtained by using the close-coupling R-matrix method. In the
calculation 19 states are included. The ionization energy of the
atomic nitrogen and the photoionization cross sections agree well
with the experimental results. Based on the R-matrix results of
atomic nitrogen, the interference effects between two neighbouring
nitrogen atoms are obtained. It is shown that the interference
effects are considerable when electrons are ionized just above the
threshold, even for the separations between the two atoms are larger
than two times of the bond length of N2 molecules. Therefore, in
hot and dense samples, effects caused by the coherent interference
between the neighbours are expected to be observable for the total
photoionization cross sections. 相似文献
3.
Importance of Relativistic Effects for Intermediate-Z Elements: Photoionization Process of Excited Na 下载免费PDF全文
Using a modified R-matrix code, the fine-structure-resolved partial photoionization cross sections of excited Na (Z = 11) are calculated within the Breit-Pauli approximation. Our calculated energy levels of Na+ and Na are in good agreement with the experimental values within 1% and the branching ratios of the J-resolved partial cross sections are consistent with the recent measurements within the experimental uncertainties. The agreements are impossible to be obtained without adequately taking into account the relativistic effects and the electron correlations together. Therefore, even for the intermediate-Z elements (e.g. Na with Z = 11), the relativistic effects (mainly the spin-orbit interactions) should not be neglected. 相似文献
4.
Density Dependence of the Detailed Spectral Line Effects on the Opacity of Astrophysical Abundant Elements: oxygen 下载免费PDF全文
A full relativistic detailed-level-accounting approach has been developed independently to deal with the detailed spectral line effects on the opacity of the third most abundant element in stars: oxygen. The atomic energy levels and the oscillator strengths of the radiative transitions between the energy levels are obtained by carrying out the full relativistic one-configuration Dirac-Fock calculations. The photoionization cross sections are obtained via an average atom scheme with a consideration for the splitting of the ionization threshold due to the ionization stages and the term-couplings. As an example, the spectra resolved opacities and the mean opacities of oxygen are calculated to show the importance of the detailed spectral line profiles with the density of the matter. 相似文献
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《中国物理 B》2016,(7)
We make a detailed study on the angular differential cross sections of positron–hydrogen collisions by using the momentum-space coupled-channels optical(CCO) method for incident energies below the H ionization threshold. The target continuum and the positronium(Ps) formation channels are included in the coupled-channels calculations via a complex equivalent-local optical potential. The critical points, which show minima in the differential cross sections, as a function of the scattering angle and the incident energy are investigated. The resonances in the angular differential cross sections are reported for the first time in this energy range. The effects of the target continuum and the Ps formation channels on the different cross sections are discussed. 相似文献
7.
Geant4 tools were used to model the single event upset (SEU) of static random access memory cells induced by heavy ion irradiation. Simulated results obtained in two different regions of incident ion energies have been compared in order to observe the SEU occurrence by energetic ions and their effects on the radial ionization profile of deposited energy density. The disagreement of SEU cross sections of device response and radial distribution of deposited energy density have been observed in both low energy and high energy regions with equal linear energy transfer (LET) which correspond to the both sides of the Bragg peak. In the low energy region, SEUs induced by heavy ions are more dependent upon the incident ion species and radial distribution of deposited energy density, as compared with the high energy region. In addition, the velocity effect of the incident ion in silicon in the high energy region provides valuable feedback for gaining insight into the occurrence of SEU. 相似文献
8.
Electron Impact Excitations and Linear Polarization for 1s2 1S0-1s2p3,1P1 Lines of Fe24+ Ions under Screened Coulomb Interactions 下载免费PDF全文
Electron impact excitation cross sections from the ground state to the individual magnetic sublevels of 1s2p 3'1P1 states in high-temperature dense plasmas are calculated for highly charged He-like Fe24+ ions by using a fully relativistic distorted-wave method. The Debye-Huckel screening model is used to screen the projectile electron from the nucleus and target electrons. The linear polarization degrees for these lines are obtained. It is found that the cross sections at all incident energies decrease with the increase of the screening for these excitations. The influence of screening on linear polarization degrees of the 1P1 line is very small. The linear polarization degrees of aP1 line decrease sharply at low incident energy with the increase of the screening. 相似文献
9.
通过对中能区和相对论能区反应总截面的比较, 可对了解核中核子密度分布的尾巴分量提供重要的信息, Glauber 模型的计算总是低估中能区的反应总截面, 对中子晕核和中子皮核, 这种低估更为严重. 因此, 基于 Glauber 模型从反应总截面提取核的大小存在着一些问题. 对一些轻的奇异核进行中能区核反应总截面的激发函数测量可能会有助于上述问题的解决.A comparison of interaction cross section at relativistic and intermediate energy provides important information about the existence of tail component in the density distribution. The Glauber model calculation always underestimates the total reaction cross section at intermediate energy. The differences are enhanced for halo and skin nuclei. The method to extract the size of nuclei via Glauber model seems to have some ambiguity. The excitation function of total reaction... 相似文献
10.
The photoionization cross sections of the levels belonging to the ground configuration [Ne]3s^2 3p^6 3d of Ge^13+ are investigated using the fully relativistic R-matrix method in the 2p - 3d excitation region. The photoionization cross section is dominated by 2p - 3d resonances. The detailed resonance structures are described and analysed with the resonance positions, widths and oscillator strengths to be determined. Good agreement is obtained between the length and velocity forms of the resonance oscillator strengths. The relative difference is less than 8%. 相似文献
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利用Dirac-Slater相对论平均自洽场理论,研究了不同原子体系光电离截面在不同核模型下的差异.考虑原子核大小时,核的尺寸效应使电子所感受到的有效核电荷减小,并进而影响到电子的概率分布及光电离截面等;对没有考虑原子核大小的点模型,由于不存在核的尺寸效应,出射光电子的波函数有较大相移,从而有可能出现Cooper极小.当入射光子的能量远大于相关电子的电离能时,不同核模型下电子束缚能及平均半径等的差异将相对减小,从而使光电离截面随入射光子能量的变化趋于一致. 相似文献
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V. A. Zilitis 《Optics and Spectroscopy》2006,101(5):661-665
The photoionization cross sections for the ground and some excited states of 11 ions of the rubidium isoelectronic sequence from Rb through Ag10+ are calculated by the relativistic Dirac-Fock self-consistent field method. The energy dependence of the photoionization cross sections and the changes in the threshold values along the isoelectronic sequence are considered. The influence of the exchange effect and the choice of gauge on the calculated values of photoionization cross sections is examined. For practical use, the calculated cross sections are approximated by an analytical expression. Along with the total photoionization cross sections, the asymmetry parameter in the angular distribution of photoelectrons and the degree of their polarization are also calculated. 相似文献
14.
在Dirac-Slater相对论理论框架下,研究了HCI(高离化态离子)的基本性质及其光电离过程的基本特征. 通常HCI的电场非常强,其电子波函数沿靠近核的径向空间被压缩,这极大地改变了相应的物质的性质,使HCI的光电离过程与一般的原子(离子)的相比较有很大的不同:原子核的尺寸效应和相对论效应变得更加重要,而多极效应对光电离截面的影响却趋于减弱. 相似文献
15.
在Dirac-Slater相对论理论框架下,研究了HCI(高离化态离子)的基本性质及其光电离过程的基本特征.通常HCI的电场非常强,其电子波函数沿靠近核的径向空间被压缩,这极大地改变了相应的物质的性质,使HCI的光电离过程与一般的原子(离子)的相比较有很大的不同:原子核的尺寸效应和相对论效应变得更加重要,而多极效应对光电离截面的影响却趋于减弱. 相似文献
16.
Plane wave Born approximation with Coulomb, relativistic and exchange corrections is employed to obtain L1-, L2- and L3-subshell ionization cross sections of several atoms due to electron and positron impacts for projectile energy varying from the threshold of ionization to 60 times the threshold energy. Photoionization cross sections for all the three L-subshells of the atoms are also calculated using the hydrogenic approximation for the atomic wave functions. For L3-subshell the present cross sections due to electron impact are in good agreement with a number of experimental data for different atoms over the entire energy range investigated. For L1- and L2-subshells the present calculations yield qualitative agreement with the experimental data. The agreement between the present results and the limited experimental data for positron impact is also satisfactory. The hydrogenic approximation for the L-subshell photoionization is found to be good at small photon energies but it underestimates the cross sections at large photon energies. 相似文献
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Liang Liang Wen-jing Gao Chao Zhou 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(16):2018-2022
Relativistic calculations of photoionization cross sections of Ne-like Cu XX using the Breit–Pauli R-matrix method in close-coupling approximation and fully relativistic distorted-wave method are reported. In the present work, the relativistic distorted-wave method is employed to calculate the fine-structure energy levels and radial functions, and the Breit–Pauli R-matrix method is employed to calculate photoionizaton cross section for photon energy from 124.2 Ryd to 208 Ryd. Resonance structure in the photoionization of Ne-like Cu XX for ejection of 2p or 2s electron from the ground 2s22p6 1S0 has been studied. 相似文献