Absolute cross sections for fast electron ejection by swift highly chargedions and evidence for "Fermi shuttle" acceleration

We report the results of recent experiments performed at the CS (Catania) a nd GANIL (Caen) cyclotron accelerators, with 45 A MeV 19(+) and 28(+) Ni-58 and 95 A MeV 18(+ 36)Ar pulsed beams, respectively Electron velocity spect ra were measured in a large angular range with different target foils (C, A l, Ni, Ag, Au). Besides electrons with the beam velocity (convoy electrons, CE) and two times the beam velocity (binary encounter electrons, BE), we o bserve also a high velocity tail in the case of the Au target only, which c an be explained by a "Fermi-shuttle" mechanism. We also give absolute BE an d CE production cross-sections. As a preliminary result of the recent GANIL experiment, we observe the lack of the CE component at the most forward an gles in the case of the carbon target. For the other targets the CE yield i ncreases as a function of the target atomic number.