EVIDENCE FOR CONVOY-ELECTRON SHIFTS DUE TO INDUCED POTENTIALS

Abstract High-resolution zero-degree electron spectra have been taken for 5 MeV/u highly-charged heavy ions (N 7+ , S 13+ , Ni 23+ and Ag 37+ ) penetrating carbon and insulator foils under normal incidence. The energy of the convoy-electron maximum has been investigated and a shift of the corresponding velocity with respect to the experimentally determined projectile velocity is found. For the carbon target there is an acceleration of convoy electrons, whereas for the insulating polycarbonate target there is a deceleration. These experimental findings are discussed in view of theoretical estimates for the dynamically ion-induced surface potentials.