A systematic comparison between born approximation and distorted wave Born approximation for inelastic electron scattering

The correction factors for Coulomb effects in inelastic electron scattering are given for electric quadrupole transitions. The cross sections in Born approximation and distorted wave Born approximation are calculated in the liquid drop model for electron energies between 20 and 80 MeV and nuclei up toZ=26.     

An exploratory study of antiproton-nucleus scattering

An exploratory study of¯p-nucleus scattering at low and medium energies (<200 MeV) is presented using optical potentials which are representative of those either derived from¯p-atomic data or calculated theoretically. The elastic differential cross sections are sensitive to the potential characteristics. Some indicative cases of inelastic scattering were also examined. Reaction cross sections are discussed and compared to recent measurements.     

The Dirac distorted wave impulse approximation revisited

Recently, we have proposed a new interpretation of the successful Dirac approach to protonnucleus elastic scattering, based on relativistic kinematics and the Lorentz-Lorenz correction. Here, we show that the Dirac distorted wave impulse approximation for low-lying collective states can be understood along the same lines. This confirms our view that relativistic effects are not the only possible explanation of the polarization data at intermediate energies.     

Semi-classical approach to antiproton-nucleus scattering

The similarities and differences between antiproton-nucleus scattering and heavyion-nucleus scattering are examined. It is found that the one-turning point approach viz Wentzel, Kramers and Brillouin (WKB) approximation can be applied to the analysis of antiproton-nucleus scattering. Using this approximation, a closed form expression for the nuclear phase shift is deduced from the corresponding expression for the heavy-ion scattering phase shift derived by Shastry and the method is illustrated by carrying out the cross-section calculation of atE _lab = 46·8 MeV.     

Distorted wave eikonal approximation for elastic electron-atom scattering

By treating the static field of the atom exactly and using the eikonal wavefunction to bring in the couplings to all remaining atomic states, a simple formula for elastic scattering amplitude is derived. Its usefulness is demonstrated by applying it to electron—hydrogen scattering.     

Usefulness of the distorted wave bound-state approximation in reaction theory

The bound state approximation (BSA) restricts the intermediate state propagation of a manybody system to specified two-cluster configurations. This approximation was tested recently by applying it to the calculation of the binding energy of the three-boson Amado model. The method was found to give poor results. We have tested the distorted wave BSA on the same model and found that the distortion can produce a great improvement.     

Intermediate annihilation states in antiproton-nucleus scattering

We study the annihilations on nuclei paying special attention to the role of unitarity in these processes. Analysing the intermediate states, it is shown that the annihilation cross section is much larger than the difference $\text{p}\text{?}\text{A ?}\text{p}\text{A}$ and for heavy nuclei is even larger than the non-annihilation cross section. The singular way in which unitarity works in annihilations can be used to test several models of particle-nucleus interactions.     

Microscopic analysis of antiproton-nucleus elastic scattering

Elastic antiproton-nucleus scattering is analysed with a microscopic optical model potential obtained by convoluting an effective interaction with target densities. Local, energy- and density-dependent complex effective interactions are constructed from reaction matrices generated with the Dover-Richard and Paris potentials. Effects of nuclear medium correction on the final results are examined. Comparison is made between the calculated results and the experimental data from LEAR which include the first polarization data as well as differential cross sections.     

库仑程函近似下扭曲因子对散射振幅的影响

在库仑程函近似框架下,引进实参量积分,将能壳上跃迁矩阵元分为靶的结构因子和弹的扭曲因子,导出了非分波扭曲因子的主项表达式和结构因子解析表达式,分析了扭曲因子对电子与类氢离子的非弹性散射角分布的影响 关键词： 库仑程函近似 散射矩阵元 扭曲因子     

Non-local small-slope approximation for wave scattering from rough surfaces

A new general analytical approach to solving the problems of wave scattering from rough surfaces, referred to as the non-local small-slope approximation (NLSSA), is suggested. It is formulated in the general form both for vector and scalar waves. This approach is valid for an arbitrary wavelength of radiation provided that the slopes of the undulations are small enough. The NLSSA represents a generalization of the small-slope approximation to situations where double scattering (in the optical sense) appears. It is demonstrated that with appropriate approximations the NLSSA of the lowest order reduces to the small-slope approximation of the second order.     

Cross sections for the rotationally inelastic scattering of Ne + N2: application of the exponential semi-classical distorted wave approximation

Exact quantum-mechanical close-coupling and approximate calculations are presented for Ne + N₂ collisions using a model potential. The approximate calculations were performed using an exponential semi-classical distorted wave approximation (ESCDW) which is outlined in the paper. The ESCDW approximation involves the evaluation of the same integrals as the standard distorted wave approximation. The former method, however, in contrast to the latter, yields a unitary S matrix and therefore conserves particle flux. The exponentiation process is shown to lead to dramatic improvements in the calculated cross sections for the present system. Cross sections evaluated using the ESCDW approximation compare very well with exact ones over the entire range of thermally accessible energies. Total and differential rotationally inelastic cross sections are presented and their variation with energy is examined. The dependence of the cross sections on the number of coupled channels included in the calculations is also investigated and a sufficient number of channels are included to ensure convergence.     

Breakup of light nuclei within the modified distorted wave Born approximation

Reactions of the elastic breakup of loosely bound light nuclei are investigated in the scope of the distorted wave Born approximation, with deuterium breakup reactions used as an example. Some drawbacks of this approximation in calculating the breakup amplitude in the prior form are shown and their causes analyzed. We propose eliminating the drawbacks by employing a modified nucleus-nucleus potential in calculating the distorted wave functions of scattering in the exit reaction channel. The calculations are compared to the experimental data.     

An analytic Voigt profile escape probability approximation

An efficient analytic Voigt profile escape probability approximation is presented and compared to exact numerical calculations. Using this analytic approximation, the two-level-atom source function is also computed for optically thick media, which have been previously evaluated exactly by Avrett and Hummer. Comparison with a more realistic laboratory plasma case also validates the usefulness of the approximation for economical modeling of radiation transport in optically thick plasmas.     

Generalizations of distorted wave impulse approximation for nuclear (π+, π0) reactions

It is shown that corrections to the ordinary distorted wave impulse approximation are uniquely important for (π⁺, π⁰) reactions in the 3,3 region and have a significant effect towards improving agreement with the existing experiments.     

An analytic approximation for the energy levels of neutral atoms

Using a screened coulomb potential, a simple formula is obtained for the shell binding energyE _ns of a neutral atom which gives accurate results over the entire range of the atomic number upto 84.     

Absorption and refraction phenomena in proton- and antiproton-nucleus scattering

The experimental data on the 180 MeV proton and 50, 180 MeV antiproton scattering by the nuclei¹²C,⁴⁰Ca and²⁰⁸Pb have been analysed on the basis of the phenomenological diffraction theory. The optical properties of the nuclei with regards to the incident protons and antiprotons are investigated. Various limiting cases of the proton- and antiproton-nucleus scattering are considered. The contribution of the Coulomb and the spin-orbit interactions to the differential cross sections of these processes has been also analysed.The authors are indebted to D.M. Skrypnik for assistance in preparing the English version of this paper.