Differential ionization measurements for electron and positron impact on atoms

Abstract
A progress report is presented on a new experimental program at the University of Missouri Rolla which is investigating the dynamics of inelastic lepton-atom collisions. By employing recoil ion momentum spectroscopie techniques, differential ionization cross sections are being studied for electron-atom and positron-atom collisions in the energy range from 50 to 1000 eV. The apparatus is configured to measure the transverse and longitudinal momentum components of the recoil target ion and of the ejected electrons. In addition, projectile scattering into θ and φ angles up to 20 degrees can be measured. The goal is to study isotachic electron and positron impact in order to investigate charge effects on the interaction dynamics. In addition, by comparing these data with existing proton impact data, mass effects can be investigated. A summary of progress to date and experiments planned for the near future are given.