Electron impact ionization of methane

Abstract

A simple model to calculate the total ionization cross sections of a molecule due to electron impact has been obtained by combining the useful features of the two previous models given by Kim and Rudd (1994 Phys. Rev. A 50 3954) and Saksena et al (1997 Physica B 233 201, 1997 Int. J. Mass Spectrom. Ion Process. 171 L1). It is shown that the Bethe and Mott cross section terms obtained by Kim and Rudd are the approximate forms of the present expressions. The calculated cross sections for the CH4 molecule are in satisfactory agreement with a number of experimental data over a wide energy range varying from 15 eV to 2.7 MeV. Although the present Bethe and Mott cross sections in the binary-encounter-Bethe model are different from the corresponding cross sections of Kim et al (1997 J. Chem. Phys. 106 1026), the total ionization cross sections obtained in these two investigations are very close to each other. For impact energies greater than about 40 eV the present cross sections are in good accord with those given by the Saksena model. However, at lower energies the present cross sections are greater than those given by the above model and are in better agreement with the experimental data. The present value of the collisional parameter is about 10% lower than the experimental value of Reike and Prepejchal (1972 Phys. Rev. A 6 1507).

High-resolution (e, 2e + ion) study of electron-impact ionization and fragmentation of methane

“…First, the ionization cross section behavior is different from the photoionization. 27,28 Second, the electron-impact ionization can result into population of excited states forbidden for photonic transitions. It can contain additional processes involving momentum transfer, post-collision interaction, and exchange, which are expected to become more pronounced for low impact energy.…”

Analysis of electron impact ionization properties of methane

“…The K‐shell ionization cross sections have also been obtained with the relativistic version of BEB model [ Santos et al , 2003] and its improved variation [ Uddin et al , 2005]. Khare et al [1999], Deutsch et al [2000], and Probst et al [2001] also calculated the ionization cross section with slightly different formulations. While these models are typically capable of reproducing experimental peak cross sections within 5%–15%, they are difficult to apply to partial ionization because they are based on collisions between a free and a bound electron.…”

Evaluation of electron impact excitation of N2 X 1Σg+(0) into the N2+ X 2Σg+(v), A 2Πu(v), and B 2Σu+(v) states

“…Many theoretical investigations have been concerned with semi‐empirical and semi‐classical formulae. Among these are the binary‐encounter‐dipole (BED) and binary‐encounter‐Bethe (BEB) models by Kim and Rudd [1994] and Hwang et al [1996], improved BED models proposed by Saksena et al [1997], Khare et al [1999], and Huo [2001], and the Deutsch‐Märk model by Deutsch et al [2000] and Probst et al [2001]. While these models are typically capable of reproducing experimental peak cross sections within 5%–15%, they are difficult to apply to partial ionization because binary‐encounter models are based on collisions between a free and a bound electron.…”