Electron impact excitation of hydrogenic ions. II

For pt.I see abstr. A12506 of 1974. The author's previously reported calculations on electron impact excitation of hydrogenic ions are extended by the inclusion of magnetic effects and retardation into the interaction between the two electrons, both the Breit and the Moller interactions being used. These effects are found to contribute 4% or less to the cross sections for Z=25 but become much larger for increasing atomic number. The effect of an improved approximation for the screening of the nucleus by the bound electron (distorted wave instead of Coulomb-Born) is also investigated and found to be small.