Elastic electron scattering by halocarbon radicals in the independent atom model approach

Sándor Demes,Eugene Remeta,Vladimir Kelemen

doi:10.1140/epjd/e2020-100529-4

Abstract

In order to study the elastic scattering of electrons by CFn (n = 1 − 4) molecular targets the independent atom model (IAM) is used with the optical potential (OP) method. The scattering cross sections were calculated in two approximations of the model – the IAM approach is used for the differential, while the Additivity Rule (IAM-AR) is used for the integral cross sections. The amplitudes of electron scattering by the carbon and fluorine atoms of the target molecules are calculated from the corresponding phase shifts, using the real and complex optical potential method. The parameter-free real part of the OP is calculated from the corresponding atomic characteristics – nuclear charge, electron density and static dipole polarizability. The differential and integral cross sections are calculated at equilibrium internuclear distances of the CFn molecules. They were compared with the available experimental data and with other theoretical results. A good overall agreement was observed while comparing our integral cross sections with the measured data. The level of the agreement however strongly depends on the target molecule, and a good consistency is observed typically above certain collision energies: from 10 eV in case of CF2, above 15-20 eV for CF3 and from 40 eV in case of CF4. Similar tendencies were found in case of the differential cross sections for a wide range of scattering angles at collision energies above 10 eV in case of CF2, above 15–20 eV for CF3, while in case of CF4 – above 20 eV.Graphical abstract

Highlights

The physical electronics is a wide scientific research area, and its achievements could be applied in several state-ofthe-art technologies: from low-temperature plasma, semiconductor production and material science up to light industry and environmental protection [1]
The scattering cross sections were calculated in two approximations of the model – the independent atom model (IAM) approach is used for the differential, while the Additivity Rule (IAM-AR) is used for the integral cross sections
We found that using the IAM-AR approach for differential cross sections (DCS) calculations leads to an intensive decreasing of cross section values at small scattering angles, compared with the results of the IAM approach

Summary

Introduction

The physical electronics is a wide scientific research area, and its achievements could be applied in several state-ofthe-art technologies: from low-temperature plasma, semiconductor production and material science up to light industry and environmental protection [1]. It is worth noting here that the experimental cross sections in [2,3] were compared with the results of several theoretical calculations They applied the Schwinger multichannel method (SMC) in the simple static-exchange (SE) approximation as well as the independent atom model with screening corrections (IAM-SCAR), both with and without ground-state dipole corrections. Nowadays more sophisticated methods are available, which treat the interaction potentials and the scattering amplitudes in a more convenient manner, taking into account purely molecular properties These models use, for example, a symmetry-adapted, single-centre expansion of the molecular wave function to calculate the electron densities. In the present work we propose a joint theoretical analysis for elastic electron scattering by the CF4 molecule and its CFn (n = 1 − 3) radicals, using two approximations of the well-known independent atom model. The cross sections in this work are compared with the available experimental and theoretical data for CFn systems

Scattering cross sections and amplitudes

Electron–atom interaction potentials

Interatomic distances of the molecules

Integral cross sections

Differential cross sections

Conclusions