Threshold Law for Electron-Atom Impact Ionization

The threshold law for electron-atom ionization is derived on the basis of the Coulomb-dipole theory. The result is a modulated quasilinear law for the yield: 2∝E(lnE)^-2[1+Csin(αlnE+μ)]. The derivation depends on a more accurate description of the dipole moment seen by the outer electron as the distance of the inner electron from the nucleus. The derivation also implies Cα^-1, and it also suggests that α is large. The same law also applies to positron-atom impact ionization.