INCLUSION OF THE GENERALIZED BREIT INTERACTION IN EXCITATION OF HIGHLY CHARGED IONS BY ELECTRON-IMPACT

The generalized Breit interaction is included in the scattering matrix elements when determining collision strengths for electron-impact excitation of highly charged ions. We use a relativistic distorted-wave approach that employs a Dirac-Fock-Slater potential to calculate the free-electron wave functions. This same potential is used to calculate the atomic-structure data. Collision strengths are presented for H-like, He-like, and Li-like ions for a range of Z values and impact-electron energies. Good agreement is obtained when comparing to the few existing calculations for hydrogenic ions. The effect of including the interaction is found to be small for ions with Z almost-equal-to 26, but increases steadily with Z. Changes of nearly 70% are observed for Z = 92. Effects for the more complex He-like and Li-like ions are greater than for the hydrogenic analogs for the entire range of Z values considered. The accuracy of some simpler forms of the Breit interaction is also discussed.