Cusp-electron production in pure-target-ionization and transfer-ionization events for 0.1-MeV/u I/sup 13+/ projectiles on He and H2 targets

Cross sections for production of electrons which are moving with near-zero velocity in the projectile frame in pure-target-ionization and transfer-ionization events were measured for 12.7-MeV I/sup 13+/ ions incident on He and H2 gas targets. These cusp-electron-production cross sections were found to be nearly equal for pure-target-ionization and transfer-ionization events in both targets. The cross section for cusp-electron production in transfer ionization from He targets comprised only 0.04% of the total transfer-ionization cross section and in pure target ionization comprised only 0.12% of the total pure-target-ionization cross section. Similar results were obtained for H2 targets except that all respective cross sections were larger than for He. The experiment shows that most of the free electrons released in pure-target- and transfer-ionization events for 0.1-MeV/u I/sup 13+/ incident on He and H2 gas targets are not low-energy electrons in the projectile frame