Coulomb deflection in ion-atom collisions

The Coulomb-deflection factor, defined as the ratio of the Coulomb to plane-wave Born cross sections, is derived for slow but classically moving ions, and found to be in agreement with the data for K-shell ionization. When the half distance of closest approach in a head-on collision, d, is comparable to the important impact parameters (~1q₀, where q₀ is the minimum momentum transfer), this factor simplifies to exp(-πdq₀) as it has been employed in the inner-shell-ionization theory. When the impact parameters are small on the scale of the projectile de Broglie wavelength, as they are in nuclear phenomena, the Coulomb-deflection factor tends to exp(-2πdq₀). An extension of our results to screened Coulomb repulsion gives good agreement with the semiclassical calculations and the data for K-shell excitation in Ne⁺-Ne collisions.