Continuum electron emission from collisions of 0.1–3.2-MeV Kr ions with Kr and Xe targets

Abstract

The electron emission spectra observed following collisions of heavy ions with heavy atoms is often dominated by electrons with a continuous range of energies. The impact-parameter dependence for the emission of these electrons from Kr-Kr and Kr-Xe collisions has been measured for collision energies from 0.1 to 3.2 MeV and for scattering angles from 3° to 10° by measuring the emitted electrons in coincidence with the scattered ions. These data indicate that most of the ionization (often 20 to 25 electrons from the collision system) resulting from these heavy-ion–atom collisions occurs during the collision on a time scale of ${10}^{\mathrm{-}16}$–${10}^{\mathrm{-}17}$ sec, as opposed to Auger decay in the separated atoms following the collision. For each combination thresholds were observed for electron production as a function of the collision’s distance of closest approach. These excitation thresholds agree well with promoted molecular orbitals calculated within the framework of the Fano-Lichten model and indicate that this model is useful beyond its expected range of applicability.