Use of local exchange potentials in the calculation of photoionization and electron-ion scattering

Several local approximations to exchange are investigated. These are compared against exact static-exchange results for $e$,${\mathrm{Li}}^{+}$ scattering and for the photoionization of the $2S$ and $2P$ state of Li. All except one are found to be fairly accurate for these cases. Calculations are also performed for photoionization of the $5D$ state of Cs, which exhibits an $f$-wave resonance. All exchange models studied for this case (including the Slater $X\alpha$) are found to give widely differing results on the position and width of this resonance. Calculations are also performed for the photoionization of the Cs $6P$ state and compared against experimental results.