Arvind Kumar Jain

Low-energy electron-SiH4 collisions using a parameter-free spherical optical potential

The authors investigate low-energy (0.1-30 eV) electron -SiH4 scattering by employing a parameter-free optical potential which is a sum of three spherical terms, namely the static, exchange and polarisation forces. The authors demonstrate that the qualitative features of the scattering parameters (such as a Ramsauer-Townsend minimum below 1 eV and a shape resonance structure around 2-3 eV) observed in recent experiments, can be very well reproduced in the present simple model. Quantitatively, the authors results (below 10 eV) are very close to the recent close-coupling calculations of Jain and Thompson (1982) and Gianturco et al (1987) using a similar kind of (but non-spherical) model optical potential. Above 10 eV, the present results are in fair agreement with experiments and are better than the earlier calculations.

Low energy elastic scattering of positrons by argon atoms

Positron scattering is complementary to electron scattering due to the difference in polarity of charge. This makes positrons an alternative tool to study atomic and molecular structure. In this paper, we report our calculations of differential and total cross sections for the elastic scattering of positrons with argon atoms in the energy range from 1 – 10 eV. A spherical optical potential approach is employed. The static potential is included exactly at the Hartree-Fock level, the short-range correlation and long-range polarization effects are target density functional and are free from any adjustable parameter. Our results are in fair agreement between experimental measurements and other theories.

L X-ray Intensity Ratios in Pb With Protons

Accelerators play a significant role in the investigation of inner‐shell ionization. Inner‐shell excitation through the impact of protons has shown renewed interest recently. These studies indicate that in the case of L‐shell ionization, most of the experiments have been conducted with protons having energies greater than 500 keV. Thus, there is not only a lack of experimental data but there also exists large discrepancies between the experimental measurements and the theoretical calculations based on different models prevailing in this energy regime. In view of this, we report in this paper the experimentally measured values of L X‐ray intensity ratios for Pb, namely, Ll/Lα, Lβ/Lα and Lγ/Lα with protons over the energy range 225 keV–400 keV using a Van de Graaff accelerator. Their energy dependence and comparison with theoretical calculations will also be discussed. These measurements have yielded data in the low energy region, which helps in the emergence of better understanding of proton induced X‐ray ...

Collision cross-sections for scattering of electrons from NO molecule

Electron-NO scattering is investigated in the energy range 2–1000eV by using a parameter-free spherical complex optical potential (SCOP) approach in the fixed nuclei approximation. The real part of the optical potential consists of three potentials namely, the static, the exchange and the polarization. For the imaginary part of the SCOP, we employ a semi-empirical model absorption potential. The molecular charge density function is calculated from a single-configuration molecular orbital based on Slater type orbitals. The various potential terms are then determined from these charge density functions. Calculations of the elastic (with and without absorption effects), total absorption, momentum transfer and differential cross-sections are obtained and compared with the available theoretical results and experimental measurements.

Investigation of L X-ray intensity ratios in Pt induced by proton collisions

A survey of literature on L X-ray parameters inspires us for taking up the present investigation. These parameters are useful to study atomic properties. In view of this, we report L X-ray intensity ratios for Pt, namely, Ll / Lα, Lβ / Lα and Lγ / Lα with proton collisions over the energy range 260 - 400 keV with an interval of 20 keV. The intention of research presented in this paper is to explore their energy dependence and comparison with theoretical calculations. These analyses will yield a data in the low energy region which assist in better clarity of proton induced X-ray emission phenomenon.

Theoretical calculation of total cross sections for e+ ? NH3 molecule at low energies

A parameter-free spherical complex optical potential model is used to calculate the differential and total cross sections for the scattering of positrons by the NH3 molecules in the energy range 10 eV − 400 eV. The optical potential is constructed from a near-Hartree-Fock one-center expansion of ammonia (NH3) wave function and it is then treated exactly in a partial-wave analysis involving variable phase approach to extract complex phase shifts. The present theoretically calculated results show good agreement with the available experimental results for total cross sections at positron energy ≥ 30 eV.

Role of Measured Vacancy De‐excitation Parameters in Proton Induced X‐ray Emission

The proton induced inner‐shell vacancy decay process is comprised of radiative and non‐radiative transitions. It is characterized by fluorescence, Auger and Coster‐Kronig yields. These studies have been evolving over the last four decades, resulting in close and stringent comparisons of the measured values with the predictions of theoretical models. In view of the present scenario, we report in this paper the role of these atomic parameters for W (tungsten) and their energy dependence. Their role in understanding this phenomenon and current progress in this regard will be highlighted. Requirements and opportunities for further effort will also be discussed.

Total (elastic + inelastic) cross sections for electron scattering with bound and free germanium and lead atoms

Spherical complex optical potential (SCOP) approach has been used to compute the differential, total (elastic + inelastic) and momentum transfer cross sections for electrons scattering from the bound and free germanium and lead atoms in the energy range from 100–5000 eV. We find that the present calculated differential scattering cross sections (DCS) exhibit all important features (such as forward peaking, dip at middle angles and enhanced backward scattering) observed in other theoretical calculations and experimental measurements. The effect of absorption potential is generally to reduce the elastic cross section.

Spin polarization and cross sections of electrons elastically scattered from heavy alkaline-earth atoms

Semi-relativistic approach is employed to compute the differential and integrated cross sections, spin polarizationP and the spin polarization parametersT andU for the scattering of electrons from barium and strontium atoms in the energy range from 2.0–300 eV. The projectile-target interaction is represented both by real and complex optical potential in the solution of Dirac equation for the scattered electrons. The real optical potential includes the static, a parameter free correlation polarization and a modified semi classical exchange potentials. The complex optical potential is constructed by adding a model absorption potential as its imaginary part to the real optical potential.