High resolution studies of electron excitation IV. The n = 3 states of helium

We present excitation and polarization functions for the n = 3 states of helium for energies between threshold and the ionization potential. In the case of the line at 501.6 nm (3 1P-2 1S) our polarization data is affected by the imprisonment of resonance radiation, but in the other cases our data is consistent with threshold values predicted by conservation of angular momentum. The excitation and polarization functions show considerable structure and we identify two of the major features which appear in all the functions as S and P resonances.