Evaluation of Electron-Impact Ionization Cross Sections for Molecules

Abstract

We describe the recent progress in the development of the semiempirical approach developed by Jain and Khare for the calculations of ionization cross sections for molecules by electron impact. Along with the state-of-the-art description of this approach, the emphasis will be on the evaluation of cross sections for a carbon dimer, C2, and trimer, C3. Single-differential ionization cross sections as a function of secondary or ejected electron energy and averaged secondary electron energy for C2 and C3 are calculated at fixed impinging electron energies of 100 and 200 eV. The integral ionization cross sections are also derived from ionization threshold to 2000 eV. Extensive comparisons of the presently evaluated direct ionization cross sections with the only available theoretical binary-encounter-dipole model calculations of Kim and Rudd, spherical-complex-optical-potential model calculations of Nagama and Antony, DM model calculations of Deutsch and Märk, and the calculations of Michelin et al. based on the combination of the Schwinger variational iterative method and distorted wave approximation revealed a satisfactory agreement. The present study also establishes the validity of the semiempirical approaches and so provides a solid foundation for further applications to the larger molecules.

Electron impact ionization cross sections of hydrogen fluoride molecule

“…The partial ionization cross section (PICS) is determined by a modified Jain-Khare semiempirical approach. [6][7][8][9][10][11][12][13][14][15][16][17][18] It gives ionization cross sections to the production of an ith type of ion in the ionization of a molecule by an incident electron of energy E, i.e. where…”

“…In this paper, we used the modified Jain-Khare semiempirical approach [6][7][8][9][10][11][12][13][14][15][16][17][18][19] to determine the different types of ionization cross sections i.e. partial and total ionization cross sections from ionization threshold to 5 KeV, partial and total single differential cross sections (SDCS) as a function of secondary electron energy at fixed incident electron energies 100 eV, 200 eV, and 500 eV, partial and total double differential cross sections (DDCS) as a function of secondary electron energy and incident angle at fixed incident electron energies 100 eV, 200 eV, and 500 eV and fixed incident angles 30 , 60 , and 90 of HF molecule and their fragmented ions.…”

Direct And Dissociative Ionization Cross Section Of Oxygen Molecule From Threshold To 10 Kev

“…And df i /dw is an oscillator strength that is a key parameter to calculate the ionization cross section (ICS). The oscillator strength can be calculated theoretically if the experimental data is not available as it is directly proportional to the photoionization cross section [17]. We have used the experimental values of absolute dipole oscillator strengths for dissociative ionization of O 2 derived by C.E.…”

“…We calculated the ICS by varying the secondary electron energy from 0 to (E-I i )/2 using equations (1) because the results are more accurate and precise at this energy. However, Satyendra Pal [17] varying this energy from 0 to (E-I i ) for partial differential cross sections. In partial ionization cross sections, if we varying secondary electron energy from 0 to (E-I i ), then results at low incident energies are more as compared experimental and all other theoretical data.…”

Early Events in Radiobiology: Isolated and Cluster DNA Damage Induced by Initial Cations and Nonionizing Secondary Electrons

“…The relatively small contribution from ionization to cluster damages becomes obvious, when we consider that in 5 ML films, about 24% and 37% of the plasmids are on average ionized twice within 20 bp by 60 or 100 eV electrons, respectively (Supporting Information). Moreover, about 59% and 55% of SEs generated by such incident electrons, respectively, lie between 5 and 12 eV (Supporting Information), as estimated from the SE distributions for organic molecules, given by Pal et al The average damage CSs of these SEs are lower than those formed at the resonance energies, , and their effective path lengths may be shorter than those of electrons incident from a vacuum. Nevertheless, their contribution to the damage produced by incident 60 and 100 eV electrons should be significant, if not dominant.…”