Second-order eikonal cross sections for the excitation of atomic hydrogen

The scheme of Wallace (Ann. Phys.; NY 78: 190 (1973)) for obtaining higher-order eikonal approximations than the Glauber approximation, is used to calculate the cross sections for the excitation of the 2s and 2p states of atomic hydrogen by electron or positron impact, correct to the second order. As expected, inclusion of the second-order term introduces differences between electron and positron scattering. For electron scattering, an estimate of the eikonal exchange amplitude has also been included. Differential cross sections are presented and discussed in the angular range 0-300, where the Wallace formula may be expected to be valid. (author)