Influence of target states on electron-impact excitation

Abstract

The collision strengths associated with excitation of the Be-like O ion by electron collision are calculated by the relativistic distorted-wave method. The so-called generalized occupation numbers are used to determine the distorted potential. We investigate in detail the influence of the target states on the collision processes. It is found that the calculated results are sensitive to the amount of valence-valence correlation included, especially for the resonance excitations to the states 2p2 1D2 and 50, in which the resulting collision strengths are enhanced by several times.