AN APPLICATION OF POLARIZED-ORBITAL APPROXIMATION TO ELECTRON IMPACT EXCITATION OF ATOMIC HYDROGEN

Two approximations for electron impact excitation of atomic hydrogen are discussed. Both include polarization effects to first order. In the first (A) a polarized Born approximation, the unperturbed ground-state target eigenfunction is replaced in the direct term of the scattering amplitude by a perturbed first-order function. The second approximation treated (B) consists of replacing the incident plane wave appropriate to Born's approximation by polarized orbitals for the incident electron. Calculations are carried out in both models, for the 1s -> 2s and 1s -> 2p transitions. In all cases the calculated cross sections lie below the corresponding Born approximation and approach it at high impact energies. In the case of approximation (B), when non-adiabatic effects are included in determining the polarized orbitals, the calculated cross sections are in good agreement with experiment near threshold (but do not give the detailed resonance structure).