Electron-impact ionization cross sections and bound-free generalized oscillator strengths for atomic systems

Abstract

Within the Born approximation, a general formulation is given for differential cross sections corresponding to electron-impact ionization of an arbitrary $L\ensuremath{-}S$-coupled atomic system. Expressions for the generalized oscillator strength and total cross section are also given. Correlation effects are explicitly included in the formulation through the use of a configuration-interaction wave function to describe the initial bound target state, and a close-coupling wave function to describe the final free target state. Two independent computer codes have been constructed which allow these functions to be of arbitrary complexity for any atom. The codes use recently developed, but different, techniques for solving the close-coupling equations. Test results are obtained for the helium atom, and they agree well with previous correlated calculations.