Abstract
The effects of allowing explicitly for exchange-polarization interactions are studied in the context of the distorted-wave polarized-orbital (DWPO) method. A modified version of earlier DWPO approximations is introduced and used to calculate differential cross sections for electron impact excitation of the n=2 level of atomic hydrogen. The results are compared with those of hybrid close-coupling methods and with absolute experimental measurements. The inclusion of exchange-polarization effects in the excitation of the S-states of helium is briefly discussed.