Identification of first order and non-first order contributions in the (e,3–1e) and (e,3e) double ionization of molecular nitrogen

Abstract

Double ionization of nitrogen molecules is investigated in coplanar asymmetric (e,3–1e) and (e,3e) experiments. The measurements are performed at intermediate incident energy (∼600 eV) with one fast scattered electron and two slower ejected electrons sharing equally the excess energy. The data are compared with the predictions of a simple kinematical model recently reported by Lahmam-Bennani et al (2010 J. Phys. B: At. Mol. Opt. Phys. 43 105201) which describes the ‘two-step 2’ (TS2) mechanism as two successive (e,2e) single ionization interactions. The model is extended to include binary as well as recoil scattering during the two successive single ionization events. It is shown to qualitatively predict the correct angular positions for most of the observed structures. Moreover, the (e,3e) data are compared with the predictions of a first Born model which fails to reproduce the experimental angular distributions. These results demonstrate that the molecular double ionization process is largely dominated by the TS2 mechanism, as was the case in our previous works on atomic targets.