IONIZATION IN COLLISIONS OF FAST H+ AND HE2+ IONS WITH FE AND CU ATOMS

A crossed-beam technique, where the collision products have been selec ted 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 pu re ionization have been determined for q = 1-4. A comparison with the corresponding (previously measured) cross sections for transfer ioniza tion shows that, in the energy range considered, Fe+ and Cu+ ions aris e predominantly through pure ionization. However, for q greater than o r equal to 2 contributions from both transfer ionization and pure ioni zation are important, Pure ionization becomes dominant at energies whi ch increase as q increases. Measured cross sections for pure ionizatio n have been successfully fitted to values based on an independent elec tron model approximation.