低能电子与氮分子碰撞振动激发动量迁移截面的研究

采用作者改进的振动密耦合方法和基于量子力学从头计算的静电势、交换势、相关极化势,研究了低能电子与N₂振动激发散射动量迁移截面. 计算结果与试验符合较好. 关键词： 动量迁移截面 低能电子 分子碰撞 振动激发     

离子极化势对钙原子共面对称(e,2e)反应影响的数值研究

本文使用扭曲波波恩近似方法(DWBA)研究了共面对称条件下钙原子的电子碰撞电离反应((e,2e)反应),在DWBA理论的基础上,考虑了原子极化势和离子极化势对三重微分散射截面的影响.采用发展的DWBA方法,我们研究了出射电子能量从6.75 e V到29.25 e V范围内电子与钙原子的碰撞电离过程,计算了电离三重微分截面.通过与已有理论和实验数据进行比较发现,离子极化势对钙原子的共面对称(e,2e)反应散射微分截面有较大的影响,很好的描述了碰撞电离微分截面的结构效应,特别是在散射角度较小时(≦60o),本文计算结果与实验测量非常一致.     

量子场论方法在电子与分子碰撞中的应用

这是一种利用量子场论所进行的探究性的研究方法,在文章中,我们设 计了一种新的较为简单的电子-原子碰撞模型,将量子场论方法与光学势方法中的可加性规 则结合起来.利用这种模型,我们计算了e-H,e-He和e-Li的微分碰撞截面,获得了较满意的 结果.     

电子在中性原子势场中的自由—自由跃迁吸收截面的理论计算

本文采用等效势模型,并基于Hartree——Fock解析波函数和X_α数值波函数计算自由电子与中性Ar和Si原子的相互作用势。用直接计算矩阵元方法和通过计算碰撞相移方法计算了电子在中性Ar原子势场中的自由—自由跃迁吸收截面,所得结果与Ashkin理论计算值符合较好,对中性Si原子亦进行了计算。通过计算说明了等效势模型对计算中性原子的自由—自由跃迁吸收截面是成功的。     

He-HF碰撞体系相互作用势及散射截面的理论研究

首先以与散射数据和实验结果符合较好的BFW势为依据,拟合了He-HF碰撞体系相互作用的ESMSV势,并与其它势进行比较,验证了拟合势的可靠性;然后采用密耦近似方法计算了不同势下He原子和基态HF分子碰撞的散射截面,并将计算结果与散射实验数据作了比较;最后研究了该碰撞体系散射截面的变化规律.研究表明:拟合势能较好地描述He-HF系统相互作用的基本特征.     

离子极化势对钙原子共面对称(e,2e)反应影响的数值研究

本文使用扭曲波波恩近似方法(DWBA)研究了共面对称条件下钙原子的电子碰撞电离反应( (e,2e)反应 ),在DWBA理论的基础上,考虑了原子极化势和离子极化势对三重微分散射截面的影响。采用发展的DWBA方法,我们研究了出射电子能量从6.75eV到29.25eV范围内电子与钙原子的碰撞电离过程,计算了电离三重微分截面。通过与已有理论和实验数据进行比较发现,离子极化势对钙原子的共面对称(e,2e)反应散射微分截面有较大的影响,很好的描述了碰撞电离微分截面的结构效应,特别是在散射角度较小时(≦60o),本文计算结果与实验测量非常一致。     

电子与原子弹性碰撞中交换势的研究

本文在用等效势模型计算电子与原子弹性碰撞的基础上,从量子力学基本原理出发,探讨了一种适用于多电子原子Li的不含参数的交换势模型,进而对e-Li弹性散射截面进行了计算,获得了较好的结果。     

类氢离子电子碰撞电离截面的扭曲波计算

在扭曲波库仑玻恩交换似近下用编制的计算程序计算了类氢离子Ｈｅ，Ｃ，Ｎｅ，Ｓｉ，Ｃａ，Ｆｅ的电子碰撞电离截面，并将结果与Ｙｏｕｎｇｅｒ的扭曲波结果作了比较。在２％以内本文的结果与Ｙｏｕｎｇｅｒ的结果一致。并详细研究了半经典交换势对电子碰撞电离截面的效应以及沿等电子数序列变化的规律     

共面不对称条件下Ar原子(e,2e)反应的三重微分截面

采用修正的扭曲波玻恩近似(DWBA)方法,计算了共面、大能量损失和小动量转移这一特殊几何条件下电子碰撞Ar(3p6)(e,2e)反应的三重微分截面.理论方法对(e,2e)反应过程近程极化势进行了修正,并引入Gamow因子表示后碰撞相互作用(PCI).将计算结果与实验结果、标准DWBA计算结果及Gamow因子修正后的DWBA-G计算结果进行了比较,发现极化效应起着重要的作用.     

低能正电子与氖,氩原子弹性碰撞截面的理论计算

本文把Khara与Moiseiwitsch极化势推广应用到多电子靶原子散射,并利用等效势模型计算了低能正电子与氖、氩原子弹性碰撞截面,我们的计算结果与别人理论计算及实验都符合的比较好。     

Optical Potential Calculation for Positron Collision with Helium

The positron-helium system is studied with the momentum-space coupled-channel optical method. The posltronium formation cross sections from the positronium formation threshold to 400 eV and total cross sections from 17 to 3000 eV are calculated. Ionization continuum and positronium formation channels are included via a complex equivalent-local optical potential in the present calculations. The results are compared with the available experimental and theoretical data.     

Elastic scattering of electrons from water molecule

This paper uses the momentum--space optical potential method to calculate the e--H₂O scattering elastic cross sections at the energy range from 6 eV to 50 eV, and the differential cross sections in the angle from 0° to 180° at 40 eV and 50 eV. The polarisation is taken into account via an emphab initio equivalent-local potential. The cross sections are compared with experimental measurements and other theoretical calculations.     

一种计算中、高能电子被分子散射总截面的修正势方法

在考虑分子内成键原子间的电子云重叠效应的基础上，提出了一种能够在中、高能区准确计算“电子-分子”散射总截面的修正势方法.利用可加性规则及Hartree-Fock波函数，使用这一修正过的复光学势，在30—5000eV内对电子被4个等电子(Z=18)分子(HCl，H₂S，PH₃和SiH₄)散射的总截面进行了计算，并将理论计算值与实验结果及其他理论值进行了比较.结果表明，利用这一修正过的复光学势及可加性规则进行计算，所得理论值与实验结果更为接近. 关键词： 电子散射 总截面 可加性规则 束缚原子     

Momentum-space optical model for K+-nucleus scattering

The momentum-space optical model of K⁺-nucleus scattering is analyzed and comparison with other conventional models is shown. The model is based on the multiple scattering formalism in which the optimal factorization approximation is used. Off-energy-shell extension of the elementary K⁺-nucleon amplitude is neglected which reduces non localities in the optical potential. Predictions of the model are sensitive to the definition of the K⁺-nucleon energy (energy shifts) but they are independent (1–2%) of a particular form of the covariant K⁺-nucleus scattering equation (relativistic Lippmann-Schwinger, Gross, Erkelenz-Holinde). The Coulomb distortion in the total cross section is important for²⁸Si and⁴⁰Ca at low momenta (≈10%). Off-energy-shell effects in the optical potential are discussed too. Results for the total and reaction cross sections are systematically below the data. The reaction cross sections are in a larger disagreement with the data than the total cross sections. This work was supported by grants ASCR A1048703 (P. Bydžovsky) and GACR 202/96/1566 (M. Sotona).     

一种考虑几何屏蔽效应的计算“电子-分子”散射总截面的可加性规则修正方法

在考虑分子内原子间的几何屏蔽效应随电子入射能量变化的基础上, 提出了一种能够在中、高能区准确计算“电子-分子”散射总截面的可加性规则修正方法. 利用这一修正后的可加性规则并使用“电子-C, H, O, N原子”散射总截面的实验数据, 在50—5000 eV内计算了电子被NO, N₂O, NO₂和C₂H₆分子散射的总截面, 且将计算结果与实验结果及其他理论结果进行了比较. 结果表明, 利用这一方法修正过的可加性规则进行计 关键词： 电子散射 可加性规则 总截面 几何屏蔽效应     

30-3000eV的正电子被O2、H2O及CH4散射的总截面计算

使用可加性规则，在Hartree-Fock水平上计算了30-3000eV的正电子被三个分子（O2、H2O及CH4）散射的总截面。计算正电子被三个分子散射的总截面时，首次使用了被束缚原子概念修正过的复光学势（这一复光学势考虑了分子中两个原子间的电子云重叠效应）。将正电子被这三个分子散射的总截面计算结果与实验结果及其它理论计算结果进行了比较，结果显示出在30-3000eV内，文中的计算结果与实验结果及其它理论计算结果具有较好的一致性。因此，可加性规则与修正后的复光学势相结合，完全适用于正电子被分子散射的总截面的计算。     

Effects of relativistic kinematics in heavy ion elastic scattering

Relativistic corrections to the reaction kinematic parameters were made for elastic scattering of ⁶Li, ¹²C and ⁴⁰Ar from ⁴⁰Ca, ⁹⁰Zr and ²⁰⁸Pb targets at incident energies between 20 and 100 MeV/nucleon. The results of optical model calculations show that the effects of such corrections are important when describing the angular distributions of elastic scattering cross sections for heavy ion scattering at incident energies as low as around 40 MeV/nucleon. The effects on the total reaction cross sections on the other hand, were found to be small within the energy range studied when the optical model potential is fixed.     

Electron impact total ionisation cross sections for simple bio-molecules: a theoretical approach

In this article, we have reported electron impact total ionisation cross sections for the bio-molecules pyridine, pyrimidine, n-propylamine, urea, formamide and N-methylformamide from ionisation threshold to 2000 eV. The present calculations are based on the spherical complex optical potential formalism and complex scattering potential ionisation contribution method. The results obtained for pyridine and pyrimidine are compared with available theoretical and experimental results and are found to be in excellent agreement with existing data. The ionisation cross sections for other molecules are reported for the first time. An interesting relation between the peak of inelastic and ionisation cross sections with target parameters is also reported. It was found that both the cross sections at their maximum depend linearly with these parameters, confirming the consistency of the values reported here.     

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.     

CDCC Approaches and Roles of Closed Channels in d-Nucleus Reactions

The effect of deuteron breakup in d-nucleus reaction is treated with the continuum discretized coupled channels (CDCC) approach, and the effects on the total reaction cross sections and elastic scattering angular distributions are studied by comparing the calculations of CDCC and spherical optical model with our global deuteron optical potential [Phys. Rev. C 73 (2006) 054605] below 200 MeV, for target nuclei ranging from ¹²C to ²⁰⁸Pb. The contributions from the closed channels to the total reaction and breakup cross sections, and angular distributions of elastic scattering are also seriously discussed.