Excitation of alkali-metal-like ions by electron impact

Differential and total cross sections for the dipole excitation of valence electrons in alkali-metal-like ions by electron impact well above the threshold energy are calculated in the generalized Born approximation and in a semiclassical approximation. The angular distribution is peaked at an angle which is essentially defined by energy-momentum-matching conditions on the classical Coulomb trajectory; around this angle, the semiclassical description is in excellent agreement with the quantal description. Deviations from the mean-field electron screening are weak and manifest themselves only in backward scattering. Semiclassical total cross sections are practically equal to the Coulomb-Born predictions. This near equality is explained within the WKB approximation. The practical equivalence between the semiclassical, WKB, and Coulomb-Born approximations applies also for other multipoles in a wide range, of energy transfer, and ionic charge