Comparison of the electron impact experimental and theoretical fourfold differential cross sections for Ne and CH4

Abstract

New measurements of the electron impact (e,3-1e) fourfold differential cross section for double ionization of isoelectronic atomic and molecular targets, namely Ne and CH4, are reported. The measurements are performed at intermediate incident energy and a different energy range for the pair of ejected electrons. We compare the experimental results with the predictions of a recently developed kinematical model (Lahmam-Bennani et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 105201), which can explain the appearance of the structures related to the second-order mechanism (such as TS2). Some of the data are compared with the predictions of the first and second Born models, showing mixed agreement. Moreover, the targets are isoelectronic hence the difference between the behaviour of the cross sections is qualitatively discussed in terms of the molecular structure influence over the ionization process.