The Coulomb-dipole theory of the e+--atom impact ionization threshold law

The Coulomb-dipole theory has recently been modified leading to a modulated quasi-linear law for both the e- and e+-atom impact ionization threshold laws. The author discusses important points which were not clear or not examined in the original derivation. These include (a) clarification of the boundaries of the Coulomb-dipole region, (b) derivation of the explicit form of the energy distribution cross section. In both cases it is found the Coulomb-dipole region is characterized by a highly modulated distribution whose envelope in the e- case is not expected to be enhanced relative to the middle (Wannier) part of the distribution for experimentally realizable energies, and (c) the threshold electron impact ionization spin asymmetry ratio is also derived and it also is found to be a highly modulated function of the energy. This prediction should provide unambiguous differences from the Wannier theory for polarized beam experiments which are being undertaken. (Auth.)