Double ionisation of helium and lithium by ion impact using independent event models

Abstract

Double ionisation is considered within the context of the impact parameter version of the continuum distorted wave eikonal initial state approximation. Starting from the independent event model, the correlation of the ejected electrons is accounted for by explicitly including the Coulomb density of states factor for the electron–electron interaction in the calculation. Total cross sections for proton, alpha particle and Li 3+ impact on helium, and proton and alpha particle impact on lithium, over the energy range 50–2000 keV/amu are presented. It is concluded that the inclusion of electron–electron correlation in the exit channel is crucial if an adequate account of the double ionisation process is to be obtained.