Absolute cross sections for projectile-charge-state-correlated multiple-ionisation processes in Ne-Ne collisions

Abstract

In the collision system Nen++Ne0+ to Nen'++neq++(n'-n+q)e-, absolute cross sections sigma (n,n',q) for the production of recoil ions were determined by a coincidence technique, in which the final charge states of the projectile (n') and the recoil ion (q) were measured simultaneously. This method permitted the investigation of the velocity dependence (at energies of 75-360 keV u-1) of different reaction channels, such as pure multiple ionisation of the target, and multiple ionisation accompanied by both capture of one or more target electrons into the projectile system and loss of projectile electrons. In the velocity range investigated here direct multiple ionisation at large impact parameters is the dominant process in creating recoil ions with low charge states (q=1,2,3), whereas highly charged ions are mainly produced in close collisions. In these symmetric collisions multiple ionisation of the projectile and the target behave quite similarly.