Abstract
For pt. III see abstr. A1025 of 1971. The convergence of the pseudo-state expansion of the electron hydrogen atom system at intermediate energies is studied. The atomic 1s and 2s eigenstates as well as 3s, 4s and 5s pseudo-states are retained in the expansion and calculations in the singlet L=0 state are carried out over incident electron energies from 10.2 eV to 30.6 eV. The 1s-2s excitation cross section is found to converge rapidly, except in the region of certain non-physical resonances and this result is used to estimate the accuracy of earlier work using the pseudo-state expansion.