Excitation of atomic hydrogen by electron impact in an on-shell Faddeev-Watson approximation

The second-order Faddeev-Watson approximation is applied to the excitation of atomic hydrogen by electron impact. By restricting the total kinetic energy of the electrons in the intermediate state to the three-body energy shell a simplification is effected when approximates the dynamics to a double Coulomb binary encounter. The resulting transition matrix elements involve multi-dimensional integrals which are evaluated numerically. Although the model fails for low momentum transfers it predicts differential cross sections and angular correlation parameters for electron-hydrogen excitation which are in reasonable agreement with experiment at high momentum transfers.