Transfer and excitation in high-energy He+-He collisions: V. Electronic continuum influence on ejected electron distributions and TE cross sections

Compared to experimental data based on 0 degrees electron spectroscopy, pre vious theoretical predictions related to simultaneous transfer and excitati on (TE) processes occurring in collisions between fast He+ projectiles and helium targets are not fully satisfactory. In fact, peaks in energy distrib utions of forward-emitted electrons have always been considered as the resu lt of the production of (bound) doubly excited states followed by post-coll isional Auger decay. However, two indistinguishable collision channels, her eafter referred to as TI, can also produce forward ejected electrons: (a) d irect target ionization and (b) simultaneous electron transfer and projecti le ionization. They are ignored in these first studies, although experiment al electron spectra show asymmetrical profiles. Here the TE process is re-e xamined within the framework of the continuum distorted wave with four-body (CDW-4B) formalism. Our approach sticks to Fano's description of a resonan ce, i.e. the adjacent electronic continuum of a doubly excited state produc ed during the collision is included. Very good agreement is found between t he present predictions and the experimental data both for energy distributi ons of ejected electrons and for so-called total TE cross sections. Further , it is shown that TE cross sections, which are extracted directly from lin eshapes, always contain non-separable contributions from the two above-ment ioned TI channels.