Cross sections for excitation and ionization in e-He(21,3S) collisions

Abstract

Cross sections for the 2³S-n³L(n=2-5, L=S-F) excitations and for single ionization in e-He(2^1,3S) collisions are determined by using the Born approximation. For a given n, the 2³S-n³D transitions dominate at intermediate energies and this trend is continued for transitions to the near continuum. For larger energies epsilon of the ejected electron, higher angular momentum l waves progressively dominate. While up to nine partial waves are in general required for convergence of the bound-free form factor, as many as 30 are needed when momentum changes are in the vicinity of the Bethe ridge for large epsilon . Binary-encounter results for ionization are also obtained and agree with the Born values at intermediate energies.