Attenuation and single electron charge-exchange cross sections of He+ on Ne and Ar in the 500--5000 eV energy range

The absolute total charge-exchange cross sections of He+ on Ne and He+ or Ar have been measured using a parallel plate target ion collection method. The first set of collision partners have large but similar ionization potentials and the resulting cross sections agree reasonably well with theory. He+ on Ar collisions appear more complex, involving many interacting states. The resulting cross section does not show good agreement with existing two-state theory. In addition, a lower limit to the total collision cross section of these same two collisions has been determined via incident beam attenuation measurements. For each of these collisions, the cross section was found to decrease monotonically with increasing ion velocity. In the He+ on Ar collision, the measured total and charge-exchange cross sections were observed to coincide at energies above 3 keV