Electron scattering by atomic hydrogen using a pseudo-state expansion I. Elastic scattering

A modified close-coupling expansion has been developed and applied to calculate elastic electron-hydrogen-atom scattering phase shifts. This expansion into a complete discrete orthonormal basis set is a variant of the more usual close-coupling expansion into eigenstates of the target Hamiltonian. We retain the first few hydrogen-atom eigenstates and augment these terms with pseudo-states chosen, in our particular case, to incorporate fully the ground-state polarizability of the hydrogen atom. The resulting phase shifts are compared, where possible, with those obtained in the most accurate variational calculations available, and they indicate a distinctly improved convergence over those obtained in the close-coupling expansion.