Der Regenbogeneffekt und Interferenzerscheinungen bei molekularen Stößen

Crossed beam measurements of differential elastic scattering cross sections for collisions of alkali atoms with mercury and xenon atoms as well as with different molecules are presented. Special attention is given to the rainbow effect including supernumary rainbows and to interference effects connected with rainbow scattering. The observation of well resolved primary and supernumary rainbows together with interference patterns make the determination of a three parameter potential model possible. Partial wave numerical calculations of differential cross sections are used to evaluate potential parameters and to discuss the limits of the semiclassical rainbow theory. Elastic scattering between reactive collision partners is investigated too and interpreted in terms of a simple optical model.     

On the separation of the nuclear and Coulomb rainbow components from the elastic scattering data

A simple wave-mechanical argument is used to separate the nuclear and Coulomb rainbow components from the experimental differential cross-section of elastic alpha and light composite particle-nucleus scattering at intermediate energies. We also show, through semi-classical arguments, how the nuclear rainbow component can be interpreted as a refractive effect due to the nuclear forces.     

重离子弹性散射中的角分散研究

简要评述了重离子弹性散射角分散研究的内容、 方法及物理意义。通过前角区重离子弹性散射产物微分截面的角分布测量,作出角分散图ln(dσ/dθ)\|θ2。 分析经典偏转函数, 从而在实验上确定了反应系统的核虹角。 在低能、 重靶的重离子反应系统中, 核虹角远小于擦边角。 晕核及弱束缚核比稳定核具有更小的核虹角和更大的核相互作用范围。 经典偏转函数的计算有助于提供一套光学势参数, 以便于拟合弹性散射产物的微分截面。 In terms of the angular dispersion plot of ln(dσ/dθ) versus θ2, which can be obtained from the angular distribution of the elastic scattering differential cross sections in heavy ion collisions, systematic analysis on the angular dispersions is made by using classical deflection function for the available experimental data on the target of 208Pb. Our systematic analyses bring about some important results. Firstly, there is an angular dispersion turning angle at forward angular range beyond the grazing angle. Secondly, the nuclear rainbow angle for such reaction systems can be determined by measuring differential cross sections of elastic scattering at forward angular range and analyzing the angular dispersion. Thirdly, analysis of angular dispersion may provide a way to determine a set of optical potential parameters by means of fitting the experimental data of elastic scattering differential cross sections. Finally, for the halo nuclei as the projectiles, there is an exotic behaviour, i. e., smaller angular dispersion turning angle.     

Effect of elastic scattering on the kinetics of mesic atom formation

The differential, total and transport elastic cross sections are calculated with an adiabatic effective (µ^––H) potential and with regard to inelastic transitions. The elastic cross section is greater than the inelastic one by an order of value in the atomic-capture energy region. The excess increases with particle mass. The effect of the elastic scattering on the energy distribution of Coulomb capture is considered within the approximation of continuous elastic energy losses. An appreciable increase of the capture probability due to elastic scattering is obtained in the low-energy region.     

0.5 eV时H++D2(v=0,j=0) 反应的微分、积分截面

基于ab initio势能面(KBNN PES)[1],用耦合通道超球坐标理论研究了碰撞能等于0.5 eV时H D2(v=0,j=0)的积分,微分截面.对于反应性碰撞,计算的积分截面表明由于深势阱的存在使得这一绝热反应产物的分布表现出一种近似的统计行为.计算的微分截面反映该体系存在着长寿命的中间络合物;对于非反应性碰撞(传能过程),平动—平动传能过程更有效,且其积分截面随着转动量子数的增大而显著减少.通过反应性碰撞和非反应性碰撞积分截面的比较,发现在低能碰撞情况,非反应性碰撞更容易进行.     

The excitation of collective nuclear states by high energy particles

The excitation of collective nuclear states by high energy particles is considered within the framework of the Glauber theory. The approach is based on the adiabatic approximation and expansion of the scattering amplitude in powers of the nonsphericity parameter. The formulae for the excitation cross sections of the rotational and one- and two-phonon vibrational states, as well as the elastic scattering cross section with the collective motion included, are obtained. The effect of nucleon correlations in both elastic and inelastic cross sections is also studied. The theoretical predictions are compared to new data on 1 GeV proton scattering by ⁵⁸Ni, ²⁰⁸Pb, ¹²C, ⁴⁰Ca and ³⁹K. A comparison with electron scattering data is simultaneously carried out. The agreement with the experimental data is generally good.     

High energy elastic and inelastic p-12C scattering and nuclear deformation

Starting from a microscopic deformed picture of the ¹²C nucleus, and using angular momentum projected wave functions, the elastic and inelastic 1 GeV p-scattering differential cross sections have been analysed within the framework of the Glauber theory. From a comparison of the results obtained in a full Glauber calculation and in the optical limit, it has been shown that the elastic scattering and, to a lesser extent, the transition to the 2⁺(4.44 MeV) level are only weakly affected by the long-range correlations. In contrast the scattering to the 4⁺(14.08 MeV) state includes crucial multi-step contributions which affect the differential cross section both in shape and magnitude. Similarly the corrections to the DWIA are essential for the transition to the 3^?(9.64 MeV) state and a satisfactory explanation of the qualitative differences observed between the 2⁺ and 3^? inelastic cross sections in ¹²C is given. The great sensitivity of the cross sections to the nuclear deformation is shown and a generally good agreement with experiment for both the electron form factors and 1 GeV p cross sections has been obtained for the ground-state intraband transitions using a single oblate intrinsic state. The importance of a correct treatment of the rotational motion through the angular momentum projection is underlined and the use of the adiabatic approxmation is critically examined.     

The Z-dependence of the elastic scattering of γ-rays

The differential cross sections for elastic scattering of 662 keV and 279 keV γ-rays from Pb, Ta, Nd, Sn, Mo, and Zn have been measured at angles ranging from 45° to 135°. The results are compared with theoretical predictions taking into account Rayleigh scattering and nuclear Thomson scattering. The theoretical Rayleigh amplitudes are based on second order perturbation theory according to Brown et al. and on form factors calculated from relativistic HFS wave functions. A semi-empirical method of correcting the form factors is developed, valid for energies between 150 keV and 750 keV and charge numbers up to Z = 82. The average difference between calculated and measured differential cross sections was found to be 6%.     

H++CO2散射在30电子伏能量下电荷转移和非电荷转移的非绝热分子动力学模拟

在大气化学、天体物理学和癌症质子疗法中都涉及到高能H⁺+CO₂散射反应.本文在最简电子-核动力学（SLEND）基础上系统研究在30 eV下的H⁺+CO₂散射.SLEND用经典力学描述核,用单行列式Thouless波函数描述电子.本文模拟了CO₂在42个取向共3402条轨线,为理解H⁺+CO₂散射中的各个反应过程和机制提供了系统描述：非电荷转移散射（NCTS）,电荷转移散射（CTS）和C=O双键的断裂,这些关于反应的有用信息不能完全从实验中获取.本文提供了散射的详尽细节,包括随CO₂取向不同主彩虹角和次彩虹角的出现和合并.SLEND NCTS和CTS的微分散射截面通过高等半经典方法计算,显示NCTS散射截面对所有散射角都同实验符合得很好,而CTS散射截面只大散射角时同实验结果符合得很好而在小角散射时稍差.无论是CTS还是NCTS SLEND都预言了主彩虹角的特征,这同实验完全一致.     

中子与52Cr反应截面的理论分析

根据中子与天然核Cr及其同位素反应的总截面,去弹性散射截面和弹性散射角分布的实验数据,获得了入射中子能量从1MeV—250MeV的一组普适中子与Cr及其同位素反应的光学模型势参数.应用光学模型,扭曲波玻恩近似理论,宽度涨落修正的Hauser-Feshbach理论,和预平衡反应的激子模型,计算和分析了中子与⁵²Cr反应的所有截面、角分布、能谱和双微分截面.理论计算与实验数据进行了分析比较.     

Low-energy electron scattering from copper

Differential cross sections for the elastic scattering of electrons from the ground states of copper for the configuration 3d¹⁰ 4s and the excitation state ²D with the configuration 3d⁹ 4s² have been calculated. Local density approximations to the exchange and correlation potentials have been used in these calculations, and it is confirmed that Hara exchange coupled with a Hedin-Lundqvist electron-gas-type correlation potential joined to an adiabatic polarization potential gives good predictions for differential cross sections. A comparison of the calculated results with other experimental and theoretical data are presented and discussed.     

Large-angle scattering of heavy ions: (II). General structure of inelastic cross section

Closed-form expressions are derived for the differential cross section of inelastic heavy-ion scattering at large angles. The inelastic transition amplitude given by the distorted-waves theory for excitation of low-lying collective states is evaluated by an extension of analytic methods developed in the preceding paper for elastic large-angle scattering. The very close relation between the inelastic and elastic cross sections is displayed. In particular it is shown that the angular distributions have a universal form, and that the backward-angle inelastic excitation function has, aside from a slowly varying overall energy dependence, an oscillatory gross structure of diffractive origin which is nearly identical to that of the elastic excitation function, irrespective of the physical mechanism involved.     

Theory of nuclear and magnetic neutron small angle scattering at dislocations in anisotropic cubic crystals

An analytic expression for the dilatation and the stress tensor in reciprocal space due to dislocations in anisotropic cubic crystals is deduced. From this absolute values of nuclear and magnetic small angle scattering cross sections are calculated. For Cu and Ni they differ considerably from the values calculated with the assumption of elastic isotropy. The new presentation of scattering theory allows further the discussion of the interference in scattering between dislocations in a dislocation network.     

Model differential cross section of elastic scattering of electrons by atoms in the Monte Carlo simulation of the passage of electrons in a substance

A new model differential cross section is proposed for describing elastic scattering of electrons in simulating the passage of electrons through a substance by the Monte Carlo method. This differential cross section correctly describes the first and second transport scattering cross sections, but is characterized by the total elastic scattering cross section much smaller than the actual value of the total elastic scattering cross section. The application of this differential cross section makes it possible to considerably reduce the number of elastic collisions in the Monte Carlo simulation of passage of electrons in a substance and to model the passage of high-energy electrons using the individual collision model.     

Differential cross sections for electron scattering by polar molecules. Elastic scattering and vibrational excitation

By use of the effective range theory for electron scattering by polar molecules differential cross sections for elastic scattering by HCN and LiF molecules and for vibrational excitation of water molecules are calculated.     

中子与裂变核238U反应双微分截面的理论分析

根据中子与原子核U及其同位素反应的总截面,去弹性散射截面和弹性散射角分布的实验数据,获得了入射中子能量0.1—20MeV的一组普适中子与U及其同位素反应的光学模型势参数.应用光学模型,核裂变理论,耦合道理论,扭曲波玻恩近似理论,宽度涨落修正的Hauser-Feshbach理论和预平衡反应的激子模型,计算和分析了中子与²³⁸U反应的所有截面、角分布、能谱和双微分截面.理论计算与实验数据进行了分析比较     

Absolute electron scattering cross sections for the CF2 radical

Using a crossed electron-molecular beam experiment, featuring a skimmed nozzle beam with pyrolytic radical production, absolute elastic cross sections for electron scattering from the CF2 molecule have been measured. A new technique for placing measured cross sections on an absolute scale is used for molecular beams produced as skimmed supersonic jets. Absolute differential cross sections for CF2 are reported for incident electron energies of 30-50 eV and over an angular range of 20-135 deg. Integral cross sections are subsequently derived from those data. The present data are compared to new theoretical predictions for the differential and integral scattering cross sections, as calculated with the Schwinger multichannel variational method using the static-exchange and static-exchange plus polarization approximations.     

Differential cross sections for muonic hydrogen scattering on hydrogen molecules

The results of first calculations of the differential cross sections for muonic hydrogen scattering on hydrogen molecules are presented. They are functions of the initial and final kinetic energy of the system and the scattering angle. These calculations are based on the respective set of cross sections for muonic hydrogen scattering on hydrogen nuclei, obtained within the framework of the adiabatic method. The Fermi pseudopotential method is used to estimate the molecular binding effects. The influence of electrons on the cross sections under consideration is described in terms of the effective screening potential. Rotational and vibrational transitions are taken into account. The calculated molecular differential cross sections show a strong angular dependence. This effect is very significant for the electronic contributions to the cross sections, e.g. for collision energies above approximately 0.1 eV only the cross sections of small scattering angles are influenced considerably by the screening. Since these differential cross sections give detailed information about the final energies and complicated angular distributions of the scattered muonic atoms they are the proper basis for calculations concerning the deceleration of muonic hydrogen atoms in molecular hydrogen targets and for Monte Carlo simulations of different experiments in muonic physics.     

中高能电子和N_2（~1∑_g~＋）、CO（~1∑~＋）弹性散射全截面的计算

此文采用由原子轨道线性组合构成的自洽场分子轨道（ＳＣＦ－ＬＣＡＯ－ＭＯ），用一级玻恩近似（ＦＢＡ）计算了能量为１００－５０００ｅＶ的电子与弹性散射的微分截面和全截面。由于采用了Ｇａｕｓｓ函数的线性组合拟合Ｓｌａｔｅｒ函数的方法（ＳＴＯ－ＫＧ），得到了弹性散射微分截面的解析表达式，使计算大大简化。计算得到的电子和Ｎ２，ＣＯ散射的总截面和实验结果进行了比较，当入射电子的能量大于１ｋｅＶ时，理论值和实验值之间符合得很好。