Positron impact ionization of He, Ne, and Ar

An ionization model containing a realistic description of the final state of the system, but employing only plane and Coulomb waves, is applied in positron ionization of helium, neon, and argon. This model was shown to agree perfectly with the earlier helium experiment of Fromme et al, for positron impact energies between 30-150 eV. Cross sections calculated with this model for impact energies up to 500 eV compare well with recent helium, neon, and argon measurements. Our work also shows that by improving the representation of the outgoing positron and electron one achieves a better agreement with the high-energy experimental cross sections.