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.     

电子被等电子分子的散射总截面的研究

讨论等电子分子的分子 (电子数Ne=10 :HF ,H2 O ,NH3,CH4 ;Ne=14:N2 ,CO ,HCN ,C2 H2 ;Ne=18:HCl,CH3F ,H2 S ,SiH4 ,C2 H6)被电子散射的总截面与其键长、键角之间的关系 ,得到了利用键长、键角计算电子被分子散射总截面经验公式 ,并与已有的拟和公式、经验公式的计算结果进行了比较     

中高能电子被分子的散射总截面与能量关系的研究

讨论了CO和CO2分子被电子散射的总截面与能量及其分子结构常数之间的关系, 证明了在不同的能量区间总截面与能量之间的关系不同, 但是在能量低于1 500 eV时可以利用键长、键角计算电子被分子散射总截面, 计算简便, 结果可靠, 并将CO2的结果与已有的拟合公式、实验数据进行了比较.     

慢电子与亚稳态He（2^3S）弹性散射中极化势研究

本采用带有截断函数的极化势,为确定其中的可调参数,给出了一个经验公式：r↑-/r0=0.618。通过慢电子与亚稳态He(2^3S)弹性散射总截面的计算,表明本确定的极化势更准确地描述了慢电子与亚稳态He弹性散射的实际过程。     

高密度体系光电离截面新表达式的应用

利用实验光谱学的Beer Lambert定律和介质中的麦克斯韦方程组，建立了精确的光吸收（光电离）截面表达式，并通过一个随体系粒子数密度和宏观复介电常数而变化的变换函数，将严格截面公式与Fano和Cooper 1968年建立的理想气体的光电离截面公式直接联系起来.建议：1)当知道某密度下正确的体系宏观复介电常数β,γ时，可直接由严格表达式求得高密度下非理想状态的正确光电离截面；2)或当知道该体系的粒子微观极化率η,ζ和其理想气体的精确截面时，用上述变换公式间接求得其他密度时的光电离截面.对氩原子和氙原子的应用表明：当缺乏β,γ时，可由某一合理的宏观电极化率物理（例如克劳修斯-莫索缔）模型来计算β,γ，从而获得高密度体系的截面.这样获得的结果符合被散射物质的光电离（光吸收）截面随体系粒子数密度增大而增加的客观散射现象.而且，考虑了高密度真实体系中粒子间相互作用的宏观电极化率模型越正确，如此求得的散射截面的误差就越小. 关键词： 光电离截面 光吸收截面 介电常数 极化率     

中高能正电子被CO，HCl，NH3及SiH4散射的总截面

利用可加性规则，使用Hartree-Fock波函数，采用由束缚原子概念修正过的复光学势(由静电势、极化势及吸收势三部分组成)，在30—3000eV内对正电子被CO，HCl，NH₃和SiH₄散射的总截面进行了计算，且将计算结果与实验结果及其他理论计算结果进行了比较.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，所得结果与实验结果的符合程度要比利用未被束缚原子概念修正的复光学势及可加性规则进行计算得到的结果好很多.因此，在复光学势中采用束缚原子概念可提高正电子被分子散射的总截面的计算准确度. 关键词： 正电子散射 可加性规则 束缚原子 总截面     

中高能量电子波NO2和SO2分子散射总截面的研究

利用可加性规则和作者最近提出的经验公式计算了能量在１０ｅＶ－１０００ｅＶ范围内电子被ＮＯ２和ＳＯ２分子散射的总截面，并对计算结果进行了讨论计算结果与已有的实验和理论结果进行了比较。     

核反应总截面参数化计算

给出了一个计算核反应总截面的参数化公式.用此公式计算了包括低能、中高能区大量系统的核反应总截面,且和实验数据进行了比较.讨论了反应总截面σ_R与中子过剩自由度(N-Z)的关系,以及相互作用半径R与轰击能量E_cm的关系.     

He-N2碰撞体系散射截面的理论研究

本文运用量子化学从头计算MP2方法6-311 G(3df,2p)基组,计算了He-N2相互作用的势能,拟合出He原子与N2分子相互作用的各向异性势函数,其势函数参数:势能球平均势阱位置、势阱深度、势能零点位置与通过散射实验数据分析的ESMSV(Exponential-Spline-Morse-Spline-Van der waals)势比较吻合.然后,用公认精确度高的密耦方法计算了He原子与N2分子碰撞体系的总微分截面、弹性微分截面、转动激发的非弹性微分截面和积分截面,计算结果与实验数据符合得较好.     

固体的光散射讲座 第四讲 非线性喇曼散射

非线性喇曼散射是指由于分子的偶极矩或激活介质的宏观极化矢量与光电场强度呈非线性关系,所引起的喇曼散射过程.在自发散射过程的理论描述中,振动着的分子体系的偶极矩可以写成其中q为分子振动的简正坐标,u为分子体系的固有偶极矩,α(q)称为分子体系的极化率,β(q)等则可称为超极化率.显然,上式中第二项所引起的喇曼散射是线性的,第三项以后各项所引起的喇曼散射则属于非线性的,其中由β(q)所引起的喇曼散射则称为超喇曼散射[1,2] 当人射光较弱时,自发的线性及非线性喇曼散射效应都非常弱,而且它们是非相干的散射.当人射的泵浦光较强时,再…     

A semi-empirical formula for total cross sections of electron scattering from diatomic molecules

A fitting formula based on the Born approximation is used to fit the total cross sections for electron scattering by diatomic molecules (CO, N₂, NO, O₂ and HCl) in the intermediate- and high-energy range. By analyzing the fitted parameters and the total cross sections, we found that the internuclear distance of the constituent atoms plays an important role in the e-diatomic molecule collision process. Thus a new semi-empirical formula has been obtained. There is no free parameter in the formula, and the dependence of the total cross sections on the internuclear distance has been reflected clearly. The total cross sections for electron scattering by CO, N₂, NO, O₂ and HCl have been calculated over an incident energy range of 10–4000 eV. The results agree well with other available experimental and calculation data.     

TOTAL CROSSS ECTIONS FOR ELECTRON SCATTERING FROM SIMPLE HYDROCARBON MOLECULES: C_2H_4,C_2H_6 AND C_3H_8

１ＩＮＴＲＯＤＵＣＴＩＯＮＳｉｍｐｌｅｈｙｄｒｏｃａｒｂｏｎｍｏｌｅｃｕｌｅｓａｓａｎｉｍｐｏｒｔａｎｔｃｏｍｐｏｎｅｎｔｉｎｔｈｅｐｌａｎｅｔａｒｙａｎｄｃｏｍｅｔａｒｙａｔｍｏｓｐｈｅｒｅａｎｄａｓａｄｏｍｉｎａｎｔｍａｔｅｒｉａｌｉｎｔｈｅｆｉ...     

Logarithmically accurate total cross sections of fast electron scattering by atoms

A simple analytical formula for the total integrated cross section of fast electron scattering by atoms is obtained. This formula, being logarithmically accurate, is derived from the approximate rule of sum that does not take into account exchange effects in the atomic wave function (Hartree approximation). It is shown that exchange effects can be neglected in that scattered electron energy range where the first Born approximation is valid. The results of calculation for He, Ne, and Ar atoms agree well with experimental data.     

Evaluation ofk ± p forward dispersion relations

Kaon-nucleon forward scattering amplitudes have been calculated from dispersion relations using recent experimental data on the total cross sections. In the unphysical region the analytical continuation of theK ^? p effective range theory has been done and for the asymptotic behaviour of the total cross sections a parametrization, suggested by the Regge-pole models, has been used. The calculated real parts of the scattering amplitude are compared with the existing experimental values, as found by the optical theorem and the extrapolation of the angular distribution to the forward direction.     

Structures in positron–atom and molecule total cross sections

Resonances in positron scattering from several atomic and molecular species are predicted by theoretical models. However, only positron–molecule binding was experimentally confirmed so far. Sharp structures in positron total cross sections were also measured; however, their detection is still in a very preliminary stage owing to instrumental limitations. Here we briefly review the present knowledge about structures in low-energy positron scattering. Based on further measurements and re-analysis of the experimental data collected at the University of Trento, we also present evidence of sharp structures in the total cross sections for several atomic and molecular targets. We find that the behaviour of some of those features can be described using the equation of a Fano resonance line-shape, despite the fact that an actual resonant scattering process might not be involved. Possible mechanisms that can give rise to such structures still need to be identified. Further independent experimental work using high-resolution spectrometers is needed in order to confirm the existence of structures in positron scattering cross sections.     

The quark model and exchange degeneracy

The quark model and exchange degeneracy of leading Reggeon contributions to quark-quark scattering amplitudes are combined for deriving a number of relations on polarizations, the real parts of forward scattering amplitudes and total cross sections. The comparison of these relations with experimental data is discussed.The authors are grateful to Ya. I.Asimov, E. M.Levin and L. L.Frankfurt for their interest in this work.     

THE STUDIES OF NON-RUTHERFORD BACKSCATTERING CROSS SECTIONS OF 4He FROM 16O

In this article, we report the 170° backscattering cross sections of ⁴He from ¹⁶O in the energy range of 2.0-9.0 MeV. Our measurements show that the alpha-oxygen scattering remains Rutherford scattering up to E_α=2.35 MeV, and there exist two energy regions, namely 5.55-5.85MeV and 8.50-8.80MeV, where the cross sections are enhanced and show a smooth variation. The measured laboratory cross sections are 9.50-9.97 and 35.0-33.0 times greater than the Rutherford values, respectively. In the 8.50-8.80MeV region, the cross sections at scattering angles of 160°, 165°, 170° and 175° were measured and found to be strongly angle-dependent. A most strong resonance occurred at 7.60 MeV, where the cross section is 200 times of its Rutherford value. This resonance has been used to measure the ¹⁶O concentration on a Cu surface, with a sensitivity of 1×10¹⁵ oxygen atoms/cm², Besides, we have studied the backscattering angle dependence of the threshold energy, i.e., the energy at which the elastic cross section begins to deviate from its Rutherford value. The experimental result seems not in agreement with the prediction made from the analytical formula developed by Bozoian et al.     

实验室动能4BeV左右的核子—核子散射

本文给出了带区近似下N-N散射振辐虚部的表示式。利用π-N低能散射的实验数据,计算了实验室动能为4BeV时带区4μ²2内谱函数对N-N散射总截面的贡献。对质子-质子散射得到和实验比较符合的结果,但是在3—4BeV.之间,中子-质子散射的总截面比质子-质子散射的总截面大得多。可以认为,这个结果表示较远的谱函数也很重要。 关键词：     

Interferenzen bei atomaren Stoßprozessen und ihre Interpretation durch ein modifiziertes Lennard-Jones-Potential

The influence of the shape of the interatomic potential on the total and differential scattering cross section, with special consideration given to interference effects, was numerically studied with the help of a 5 parameter modified Lennard-Jones potential. It is shown that the experimental data for the systems Na-Kr and Na-Xe, for which precise measurements are available, can be well reproduced with the use of such a potential. The absolute value and velocity dependence of the total scattering cross section as well as rainbow scattering and rapid oscillations in the differential scattering cross section were all used in the comparison of the calculated with the experimental values. In addition, the modified potential has been used in a re-evaluation of recent experimental results for alkali metal —inert gas scattering.