ELECTRON-IMPACT EXCITATION AUTOIONIZATION OF THE (2S(2)S-1, (2P(2))D-1 AND (2S2P)P-1 AUTOIONIZING STATES OF HELIUM

The electron impact excitation of the (2s2)1S, (2p2)1D and (2s2p)1P au toionising states of helium and their subsequent radiationless decay w as studied by observation of the ejected electrons. The present work w as carried out at an incident energy of 94.6 eV and for ejected electr on scattering angles in the range 25-135-degrees. This study was condu cted simultaneously with an (e,2e) investigation into thewe same autoi onising states with the results of this latter work being discussed el sewhere. The lineshapes observed in the present ejected electron spect ra are analysed using the Shore-Balashov parametrisation. As part of t he analysis procedure we determine numerically rigorous confidence lim its for the derived parameters. We believe this is the first time that such error limits are presented in the literature for the derived par ameters No previous experimental or theoretical work has been undertak en at the incident energy of the present investigation but, where poss ible, the resulting parameters are qualitatively compared against the 80 eV results of other experiments and theory.