Exchange corrected Eikonal-Born approximation for elastic scattering of electrons by Helium

Differential cross-sections for elastic scattering of electron from Helium atom have been calculated using the Eikonal-Born Series method with the inclusion of exchange effect evaluated by Glauber Model. The results obtained for 300 eV incident electrons are compared with other theoretical calculations and with recent experimental data.     

Elastic scattering of positrons by helium and lithium

We present differential and integrated cross-sections for elastic scattering of positrons by helium and lithium at intermediate and high energies, calculated using the two-potential eikonal approach. The present calculations are compared with the available theoretical results.     

Elastic scattering of e∓ by Na atoms

ABSTRACT

The differential, integrated elastic, momentum transfer, viscosity and total cross-sections along with Sherman function for the elastic scattering of electrons and positrons by sodium atoms have been calculated within the framework of complex projectile–atom optical potential model at the impact energies 0.1 ≤ E_i ≤ 10⁴ eV for both the projectiles. The relativistic Dirac partial wave techniques, with accurate analytical charge densities, are used to obtain the scattering amplitudes. The present results produce satisfactory agreement with the experimental measurements and other theoretical calculations available in the literature.     

Symmetric scattering ine ±-H ionization collisions

Triple differential cross-sections for ionization of hydrogen atoms by electrons and positrons have been calculated for symmetric coplanar geometry following a multiple scattering method suggested and used earlier by the authors. Results show single binary peaks exactly at 45° and double binary peaks exactly at 135° for higher energies as are expected from an analysis of Briggs [3]. At lower energies there are certain deviations from these values. An analysis of scattering mechanism at peaks are also given. This supports Briggs’ explanation.     

High energy elastice + − O2 scattering

Theoretical differential cross-sections are obtained for the elastic scattering of fast (E _i ⩾ 200 eV) positrons by oxygen molecules. Employing the independent atom model, the atomic scattering amplitudes are calculated with the (static + polarization) model potentials, in the partial wave analysis (PWA). Comparisons made with the theory and experiments on the incident electrons, show significant differences at small angles.     

Elastic and total cross-sections for electron scattering by acetylene in the intermediate energy range

We present a joint theoretical-experimental study on electron scattering by C₂H₂ in the intermediate energy range. We report calculated elastic differential, integral, and momentum-transfer as well as total (elastic + inelastic) and absorption cross-sections at impact energies ranging from 10 to 500 eV. Also, experimental absolute elastic cross-sections are reported in the (50-500)-eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics. The iterative Schwinger variational method, combined with the distorted-wave approximation, is used to solve the scattering equations. Experimentally, the angular distributions of the scattered electrons are converted to absolute cross-sections using the relative flow technique. The comparison of our calculated with our measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.Received: 26 August 2004, Published online: 5 October 2004PACS: 34.80.Bm Elastic scattering of electrons by atoms and molecules     

Elastic scattering of electrons by hydrogen atom in a laser field

The cross-sections for the elastic scattering of electrons by hydrogen atoms in the presence of a laser field have been calculated in the Glauber and the Born approximations. The Born approximation has been found to underestimate the cross-sections and the increase of the intensity of the electromagnetic field is found to lower the cross sections.     

Glauber exchange amplitudes for electron-helium scattering

An exact closed form expression is obtained for the Glauber-Bonham-Ochkur exchange amplitudes for the electron helium scattering. The results thus obtained are compared with the results from Ochkur approximation and are used further for obtaining closed form expressions for the differential and total exchange cross-sections for the elastic scattering of electrons from the ground state of helium atom.     

Elastic scattering of electrons by hydrogen molecules

Elastic scattering of electrons by hydrogen molecules has been investigated in the intermediate energy range 100–2000 eV. The direct scattering amplitude consists of first Börn and second Börn minus distortion term. The contribution of exchange has been included through Ochkur approximation. The elastic differential cross-sections agree with experimental data.     

Differential and integral cross-sections of e-O<Subscript>2</Subscript>, O<Subscript>3</Subscript>, NO,CO scattering at energies 100–1000 eV

A modified additivity rule is formulated to calculate the differential cross-sections for elastic scattering of electrons from molecules. It improves the results at small angles and at relatively lower incident energies (<1000 eV). Integral cross-sections calculated presently are combined with the known total ionization cross-sections to obtain total (complete) cross-sections. An extension of the present approximation to larger molecules is also suggested.     

Die Reichweite von Elektronen und Positronen kleiner Energie in Kupfer,Silber und Gold

In continuation of previous work the range of 40 to 160 keV monoenergetic electrons and positrons in copper, silver, and gold is determined and the corresponding range-energy-relations are stated. In copper the positrons have a shorter range than electrons of the same energy, but in silver and gold they have a longer range, in disagreement with the values calculated byNelms 2. For the three absorption materials all the ranges of electrons can be described by the formula E^?=14,3 · (Z^4/3/A) · R^{0, 61}, and all the ranges of positrons by E⁺=29,7 · (Z/A) · R^{0, 60} (E in keV, R in mg/cm²). The ratio of the range of positrons to that of electrons for copper agrees rather well with the calculated one, but for silver and gold it differs considerably. This might be due to the increasing influence of the elastic scattering of the particles on nuclei.     

Elastic scattering of electrons and positrons by cadmium atoms

ABSTRACT

The differential, integrated elastic, total and momentum transfer cross sections along with Sherman function for the elastic scattering of electrons and positrons by cadmium atoms have been evaluated from the partial wave solution of the Dirac relativistic scattering equations for a projectile-atom complex potential at the energy range 6.4 eV < E < 1.0 keV. For various scattering quantities, a comparison of our results exhibits better agreement with the experimental data than the other available theoretical values.     

Effects of Ps polarization potentials on Ps total cross-sections of the collisions of positrons with alkali metal atoms and alkaline-earth positive ions

Summary The previous form of the coupled-static approximation applied to the inelastic scattering of positrons by alkali metal atoms is improved by switching on the polarization potentials of the positroniums. The effect of these potentials on the total elastic and positronium formation cross-sections of three different scattering problems (namely the collisions of positrons with lithium, sodium and potassium atoms) is discussed in details. Particularly, we devote our interest to the comparison between the resultant positronium formation cross-sections and those of the inelastic collisions of positrons with berylium, magnesium and calcium positive ions.     

Elastic scattering of electrons from tetrahydrofurfuryl alcohol

Differential cross-sections (DCSs) for elastic scattering of electrons from tetrahydrofurfuryl alcohol (THFA), which can be considered as an analogue molecule to DNA sugar deoxyribose, were determined using crossed beam measurements for incident energies from 40 eV to 300 eV and scattering angles from 30° to 110°. The relative DCSs were measured both as a function of incident electron energy and scattering angle, allowing absolute calibration of the whole data set via normalization to a single point. The absolute calibration has been performed according to calculated absolute DCSs obtained by the corrected independent atom method using an improved quasifree absorption model. The calculated data-set includes DCSs and integral elastic and inelastic cross-sections in the incident energy range from 5 eV to 5000 eV. The theoretical results agree very well with the experimental ones, regarding the shape of DCSs. Moreover, the same theoretical procedure has been used to obtain DCSs for elastic electron scattering from a simpler deoxyribose analogue tetrahydrofuran (THF), which agree very well, both in shape and on the absolute scale, with the recent experimentally obtained absolute DCSs [A.R. Milosavljević et al., Eur. Phys. J. D 35, 411 (2005)]. The present results are also compared with the recent theoretical data for THF and THFA. Finally, according to both experimental and theoretical data, the DCSs for elastic electron scattering from THFA and THF molecules appear to be very similar both in shape and absolute scale.     

Total (complete) and ionization cross-sections of argon and krypton by positron impact from 15 to 2000 eV – Theoretical investigations

Considering interactions and scattering of positrons with argon (Ar) and krypton (Kr) atoms, we have calculated total cross-sections (Q _T?=?Q _el?+?Q _inel ) using complex spherical potentials for these systems. In positron?Catom scattering it is difficult to bifurcate the ionization and cumulative excitation contained in the total inelastic cross-section. An approximate method called CSP-ic (complex scattering potential-ionization contribution) similar to electron?Catom scattering has been applied to bifurcate ionization and cumulative excitation cross-sections at energies from the threshold to 2000?eV. Adequate comparisons of the present results are made, with available data.     

On validity of the weak interaction renormalizable theory of Tanikawa-Watanabe

It is shown that the weak interaction renormalizable theory of Tanikawa-Watanabe, which in its simple formulation predicts essential effects in (e^±p) scattering, contradicts the experimental data on elastic scattering of electrons and positrons on protons if the existing concepts on the role of the two-photon exchange in these processes are valid.     

Elastic and inelastic scattering of positrons from hydrogenlike ions

Summary The total elastic cross-sections of the collisions of positrons with various hydrogenlike targets (with nuclear chargeZ=1, 2, 3, 4, 5 and 11) are determined at 13 values of the incident energy lying below 6.8 e V(the positronium formation threshold of e⁺-H scattering). The inelastic scattering of positrons by the same targets is investigated for the first time at energies above the positronium formation thresholds. Both scattering processes are treated using a coupled-static formalism and an iterative Green's function partial wave expansion technique. The resulting cross-sections demonstrate the stability of this technique and emphasize the importance of exploring the aspects of positron-ion collisions more fundamentally on both theoretical and experimental levels.     

Spin polarization of electrons elastically scattered from europium and bismuth atoms

We present calculations of differential, integrated elastic, total, momentum transfer cross-sections and spin-polarization parameters S, T and U for scattering of electrons from Eu and Bi atoms in the energy range 2.0 to 500.0 eV using semi-relativistic approach. The target-projectile interaction is represented both by real and complex parameter-free optical potentials in the solution of Dirac equation for the scattered electrons. The results for the differential cross-sections and spin-polarization parameters have been compared with the available calculations and experimental results. Received 17 February 2000 and Received in final form 15 June 2000     

Electron impact ionization of Zn+ and Ga+

We have investigated the contribution of excitation-autoionization to the electron impact ionization of Zn⁺ and Ga⁺ using the binary encounter approximation. Hartree-Fock velocity distributions for the bound electrons have been used throughout the calculations of direct and indirect ionization cross-sections. The calculated cross-sections are in good agreement with recent experiments. We have also compared our results with other theoretical calculations.