Ejected electron spectrum of He below the N=2 threshold

Electron-impact ejected electron spectra of He below the He+ N=2 threshold have been measured for all combinations of incident energies 550, 150, and 75 eV and ejected electron directions 60°, 90°, and 120° with respect to the incident electron beam direction. Autoionizing levels from the four main series S0e1, P1o3, D2e1, and P1o1, are observed up to n=7, and resolved up to n=5. In addition several weak members of other series are observed. The positions, and in some cases the widths, are tabulated for 30 levels, and these are compared with theoretical and other experimental values.