(e, 2e) experiments on (2s(2))S-1, (2p(2))D-1 and (2s2p)P-1 autoionizing levels of helium in the direction of the binary lobe

The (e, 2e) triple differential cross sections are measured for the electron-impact excitation of the (2s(2))S-1, (2p(2))D-1 and (2s2p)P-1 autoionizing transitions in helium. The experiments were performed under coplanar asymmetric kinematics, at an incident electron energy of 250 eV, and for a scattered electron detection angle of -13 degrees. in the direction of the binary lobe. The results are compared with the two available experimental data sets under similar kinematical conditions, consequently removing questions raised by the theory on these earlier results. We present evidence that the spectrum for the (2p(2))D-1 and (2s2p)P-1 states might be dependent on the energy resolution of the scattered-electron energy analyser, especially in the binary region, where the strong interference between the two processes results in the observed broad asymmetric profiles. This possible distortion is not solely related to the present work.