Calculations of Electron Impact Ionisation Cross-sections

Abstract

In the present work, the electron impact ionisation cross-section calculations has been carried out for various atoms, ions and molecules. Using Lotz formula the electron impact ionisation cross-sections are presented for 28 atoms and ions, out of which 20 are either atoms or singly charged ions and the rest 8 are multicharged ions. FORTRAN programs for calculating the electron im pact ionisation cross sections for different atoms and ions were made. Based on obtained results the graphs of the energy of the incident electron versus cross sections were made and are presented here. The theoretical cross-sections plots thus obtained were compared with the experimental data wherever available. Similarly the electron impact ionisation cross-sections of some of the atoms have also been calculated using the Binary Encounter Bethe(BEB) method. The cal culations of the cross sections by Lotz formula and the BEB method were done to test the reliability and the accuracy of the formulae so that one can have an idea that which method is better which provides good agreement with the experimental data. The BEB method is also applied here to obtain electron impact ionisation cross-sections of some of the molecules. For this calculation also the comparison with the experimental data is done wherever available. For the calculation of electron impact ionisation of atoms by the BEB method the binding energies and the internal kinetic energies were taken from NIST stan dard database [1],[2]. The elecron impact ionisation cross-sections of 8 atoms calculated by the BEB method are presented here and compared with the re sults obtained from the Lotz formula and also the experimental data wherever available. The ionisation cross-sections of some of the molecules are also pre sented here which have been obtained using the BEB method. Since the data required for BEB method for internal kinetic energy and the binding energies of the molecules presented here were not available therefore we have calculated the same with the help of Gaussian software package using the Hartree-Fock theory or the density function theory.