Differential cross sections for H 2s-3s excitation by electron and positron impact

Electron and positron impact differential cross sections for excitation of the 3s state of a hydrogen atom from its metastable 2s state are calculated in a distorted wave approximation at 10 and 50eV. The effects of both adia batic and non-adiabatic distortion of the atomic charge cloud by the incomi ng electron or positron are included in the initial and final state wavefun ctions. Contrary to an earlier prediction, no dramatic differences between the electron and positron results are found.