Electron impact excitation of H and He+. I. 1s to ns transitions

A polarized orbital distorted wave model is used to calculate total and differential cross sections for 1s to ns(n=2,3,4,5) electron impact induced transitions in H and He + from threshold to 20 Ryd. The total cross sections for the 1s to 2s transitions are in good agreement with experiment, but cannot in this model show resonances. The differential cross sections at energies above 100 eV agree closely with those of Geltman and Hidalgo (1971). The model reduces to the Born-Oppenheimer (z=0) or CBO I(z=0) when the polarization and static potentials are omitted.