Ionization in collisions of fast H+ and He2+ ions with Fe and Cu atoms

Abstract

A crossed-beam technique, where the collision products have been selected by time-of-flight (TOF) spectroscopy with either a pulsed beam or coincidence counting, has been used to study pure ionization of Fe and Cu by 70-1440 keV amu-1 H+ and 35-425 keV amu-1 He2+ ions. Cross sections for the formation of q times ionized Fe and Cu products by pure ionization have been determined for q=1-4. A comparison with the corresponding (previously measured) cross sections for transfer ionization shows that, in the energy range considered, Fe+ and Cu+ ions arise predominantly through pure ionization. However, for q>or=2, contributions from both transfer ionization and pure ionization are important. Pure ionization becomes dominant at energies which increase as q increases. Measured cross sections for pure ionization have been successfully fitted to values based on an independent electron model approximation.