低能电子与H_2分子碰撞振动激发动量迁移散射截面的研究

采用振动密耦合方法及基于量子力学从头计算的静电势、交换势和相关极化势,研究了低能电子与H2分子碰撞振动激发的动量迁移散射截面.通过包含18个振动波函数、8个分波和16个分子对称性,得到了收敛性很好的ν=0→ν′=0,1,2,3,4等几个振动跃迁通道的动量迁移散射截面值,并在入射电子能量1eVE≤10eV时给出了比以前的理论研究更为合理的总的动量迁移散射截面.     

异二氯乙烯价壳层轨道电子结构的电子动量谱研究

本文报道了异二氯乙烯分子价壳层轨道电子结构的电子动量谱研究.实验由一台(e,2e)电子动量谱仪在非共面对称的几何条件下开展,入射电子能量为1200 eV.实验获得了异二氯乙烯价壳层各个轨道的电离能谱和电子动量分布.采用Hartree-Fock方法和密度泛函方法结果与实验数据基本一致.研究发现,干涉效应会对2a_2和5b_2这两个Cl孤对电子轨道的电子动量分布产生显著影响.     

异二氯乙烯价壳层轨道电子结构的电子动量谱研究（英文）

本文报道了异二氯乙烯分子价壳层轨道电子结构的电子动量谱研究.实验由一台(e,2e)电子动量谱仪在非共面对称的几何条件下开展,入射电子能量为1200 eV.实验获得了异二氯乙烯价壳层各个轨道的电离能谱和电子动量分布.采用Hartree-Fock方法和密度泛函方法结果与实验数据基本一致.研究发现,干涉效应会对2a_2和5b_2这两个Cl孤对电子轨道的电子动量分布产生显著影响.     

计算中低能量电子与水分子弹性散射微分截面

运用耦合通道光学势方法计算了在中低能量下的电子与水分子碰撞弹性散射微分截面,其中靶的极化效应被包含在一个从头算的等价局域势中.随后将计算结果与实验值和其它理论计算结果进行了比较.结果显示这种计算方法对于电子与极化分子体系碰撞是非常适用的.     

电子碰撞分子的R-矩阵研究

采用R-矩阵方法首次研究了电子碰撞激发S3分子过程.S3分子靶态采用24个电子态密耦合表示,计算了电子碰撞由基态1A1平衡位置垂直激发到电子激发态13B2,13B1,13A2,11A2和11B1的积分散射截面.     

用振动密耦合方法研究低能电子与N2分子碰撞的振动激发微分散射截面

采用振动密耦合方法,分别应用球高斯分布极化势和优于绝热极化势,及基于量子力学从头计算的静电、交换势,得到入射电子能量2.40eV时0→2和0→3的振动激发微分散射截面,与目前优秀的实验值比较,获得了满意的结果,并从理论上分析了整个计算过程中可能影响微分散射截面精度的主要物理因素. 关键词： 分子碰撞 微分散射截面 振动激发 相互作用势     

低能电子在水介质中的输运过程

考虑到低能电子(能量下限为1eV)在水中输运时的电离,激发,俘获以及超激发引起的自电离等非弹性散射机制,并且考虑到OH⁺,H⁺等自由基的产生和分布,运用Monte Carlo方法模拟了电子在水中输运的径迹结构,揭示了电子在低能情况下输运时单条轨道的空间分布结构特点(云团,团点和短径迹等空间分布实体)和包含在大量轨道中的径迹结构的统计性质,并通过对比截止能量取30和1eV两种情况,分析了30eV以下的低能电子的作用.     

低能电子与N2分子碰撞的振动共振激发散射截面的密耦合研究

使用经孙卫国教授改进后的振动密耦合散射方法和基于量子力学从头计算得到的静电、交换与极化散射作用势,研究了低能电子与N2分子的振动激发散射截面.研究表明在振动密耦合计算中使用18个振动波函数和12个分波数目,可以得到收敛的0→5,1→5等高激发散射的积分和微分截面.     

低能电子与Kr、Xe弹性碰撞截面的计算

本文利用原子的解析波函数,导出了电子与第四,五周期元素原子相互作用势的解析形式,并用文献提出的物理模型与计算方法,对低能电子被Kr和Xe散射的截面进行了计算,得到了入射电子能量从0.01eV到100eV范围内弹性散射总截面,动量转移截面和微分散射截面的大量数据。计算结果与实验符合得很好。同时利用计算的结果,对低能电子被惰性气体原子散射的规律性进行了探讨。     

低能O3+与H2碰撞电子俘获过程中靶的同位素效应研究

利用全量子的分子轨道强耦合方法,我们研究了基态的O3 (2s22p2P)与氚分子和氢分子碰撞的电荷转移过程,计算了方位角为45°,能量分别为0.1eV/u,1.0eV/u,100eV/u,500eV/u的单电子俘获的振动分辨的态选择截面及总截面.分子轨道强耦合计算中采用了自旋耦合价带理论计算的三原子分子势能面和径向耦合矩阵元.对体系的电子运动同H2(T2)或H2 (T2 )的转动和振动之间的耦合,根据能量的不同,分别采用了无限阶的冲量近似或振动冲量近似.结果发现,低能O3 与H2碰撞电子俘获过程中靶的同位素效应显著:对不同的同位素靶,单电子俘获的总截面以及振动分辨态选择截面的分布明显不同;入射离子能量越低,同位素效应越显著.     

Elastic electron scattering with CH2Br2 and CCl2Br2: The role of the polarization effects

We present elastic electron scattering cross sections with holmethane molecules CH₂Br₂ and CCl₂Br₂ in the low-energy region ranging from 0.01 eV to 20 eV. The calculations are performed with the R-matrix method in static-exchange plus polarization (SEP) and close-coupling (CC) approximations. The integral, differential, and momentum transfer cross sections are calculated. The convergence of the obtained cross sections is checked at four different levels of SEP approximation. The predicted positions of the resonances agree well with available results. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. We find that the polarization has a substantial effect on the cross sections, and this effect becomes even more important for lower impact energies.     

A Correlation Potential Method for Electron Scattering Total Cross Section Calculations on Several Diatomic and Polyatomic Molecules over Energy Range 10 ～ 5000 eV

A complex optical model potential correlated by the concept of bonded atom, which considers the overlapping effect of electron clouds between two atoms in a molecule, is firstly employed to calculate the total cross sections for electron scattering on several molecules (NH₃, H₂O, CH₄, CO, N₂, O₂, and C₂H₄) over the energy range 10～5000 eV using the additivity rule model at Hartree-Fock level. The difference between the bonded atom and the free one in states is that the overlapping effect of electron clouds of bonded atoms in a molecule is considered. The quantitative total cross sections are compared with the experimental data and with the other calculations wherever available and good agreement is obtained over the energy range 10～5000 eV. It is shown that the correlated calculations are much closer to the available experimental data than the uncorrelated ones at lower energies, especially below 500 eV. Therefore, considering the overlapping effect of electron clouds in the complex optical model potential could be helpful for the better accuracy of the total cross section calculations of electron scattering from molecules.     

Elastic cross sections for electron--carbon scattering

We used the close-coupling optical (CCO) approach to investigate the open-shell carbon atom. The elastic cross sections have been presented at the energies below 90eV, and the present CCO results have been compared with other theoretical results. We found that polarization and the continuum states have significant contributions to the elastic cross sections. The present calculations show that the CCO method is capable of calculating electron scattering from open-shell atoms.     

Total Cross Sections for Electron Scattering on Polyatomic Molecules (CH4, CO2,NO2, and N2O) at 10 ～ 3000 eV

A new modified formulation of the Additivity Rule (AR) was proposed to calculate the total electron scattering cross sections for CH₄, CO₂, NO₂, and N₂O, considering the overlapping between atoms in molecules and the not fully transparency of the molecules. The present calculation covers the range of impact energy from 10 to 3000 eV. The results are compared with experimental data and other theories where available. The atoms are presented by spherical complex optical potential, which is composed of static, exchange, polarization, and absorption terms.     

Total Cross Sections for Electron Scattering from CF4, CF3H,CF2H2, and CFH3 Molecules in Energy Range from 100 to 3000 eV

The additivity rule has been employed to calculate the total cross sections for electron scattering by CF4,CF3 H, CF2 H2, and CFH3 molecules over an incident energy range from 100 to 3000 e V. Compared with other calculations and experimental data for CF4, excellent agreement has been obtained. Above 1000 eV, there are no experimental data for CF3H, CF2H2, and CFH3, so the present results can provide comparison and prediction for experimental research.     

Study of ion desorption induced by a resonant core-level excitation of condensed H2O using Auger electron photo-ion coincidence (AEPICO) spectroscopy combined with synchrotron radiation

Ion desorption induced by a resonant excitation of O 1s of condensed amorphous H₂O has been studied by total ion and total electron yield spectroscopy, nonderivative Auger electron spectroscopy (AES) and Auger electron photo-ion coincidence (AEPICO) spectroscopy. The spectrum of total ion yield divided by total electron yield exhibits a characteristic threshold peak at hν = 533.4 eV, which is assigned to the 4a₁ ← O 1s resonant transition. The AES at the 4a₁ ← O 1s resonance is interpreted as being composed of the spectator-AES of the surface H₂O, and the normal-AES of the bulk H₂O, where the 4a₁ electron is delocalized before Auger transitions. H⁺ is found to be the only ion species in AEPICO spectra measured at the 4a₁ ← O 1s resonance and at the O 1s ionization (hν = 560 eV). The electron kinetic energy dependence of the AEPICO yield (AEPICO yield spectrum) at the 4a₁ ← O 1s resonance is found to be greatly different from that at the O 1s ionization. The peak positions of the AEPICO yield spectrum at the 4a₁ ← O 1s resonance are found to correspond to those of the spectator-AES of the surface H₂O, which is extracted from the AES at the 4a₁ ← O 1s resonance. Furthermore, the AEPICO yield is greatly enhanced at the 4a₁ ← O 1s resonance as compared with that at the O 1s ionization. On the basis of these results, a spectator-Auger-stimulated ion desorption mechanism and/or ultra-fast ion desorption mechanism are concluded to be responsible for the H⁺ desorption at the 4a₁ ← O 1s resonance. The enhancement of the H⁺ yield is ascribed to the O---H anti-bonding character of the 4a₁ orbital.     

Nonlocal Optical Spatial Soliton with a Non-parabolic Symmetry and Real-valued Convolution Response Kernel

Based on the picture of nonlinear and non-parabolic symmetry response, i.e., Δn₂(I)≈ρ(a₀+a₁x-a₂x²), we propose a model for the transversal beam intensity distribution of the nonlocal spatial soliton. In this model, as a convolution response with non-parabolic symmetry, Δ n₂(I)≈ρ(b₀+b₁f-b₂f² with b₂/b₁>0 is assumed. Furthermore, instead of the wave function Ψ, the high-order nonlinear equation for the beam intensity distribution f has been derived and the bell-shaped soliton solution with the envelope form has been obtained. The results demonstrate that, since the existence of the terms of non-parabolic response, the nonlocal spatial soliton has the bistable state solution. If the frequency shift of wave number β satisfies 0<4(β-ρb₀/μ)<3η₀/8α, the bistable state soliton solution is stable against perturbation. It should be emphasized that the soliton solution arising from a parabolic-symmetry response kernel is trivial. The sufficient condition for the existence of bistable state soliton solution b₂/b₁>0 has been demonstrated.     

He原子与HI分子碰撞截面的密耦计算

基于发展的分子间相互作用势, 采用密耦方法计算了入射能量从1到140?meV范围内He原子与HI分子碰撞的微分截面、分波截面和积分截面.通过与He-HX（X=F,Cl,Br）体系分波截面的比较, 印证了He-HI体系相互作用势以及密耦计算结果的可靠性.结果表明：小角散射的概率大于大角散射的概率;碰撞能量越高,散射概率就越小, 尾部效应也越弱.总积分截面主要来自弹性碰撞的贡献;非弹性积分截面以00→01和00→02跃迁的贡献为主,其中00→02跃迁的贡献最大. 关键词： 碰撞截面 密耦计算 HI-He体系     

Mechanisms of photo double ionization of helium by 530 eV photons

We have measured fully differential cross sections for photo double ionization of helium 450 eV above the threshold. We have found an extremely asymmetric energy sharing between the photoelectrons and an angular asymmetry parameter beta approximately 2 and beta approximately 0 for the fast and slow electrons, respectively. The electron angular distributions show a dominance of the shakeoff for 2 eV electrons and clear evidence of an inelastic electron-electron scattering at an electron energy of 30 eV. The data are in excellent agreement with convergent close-coupling calculations.