Low-energy electrons and their dynamical correlation with the recoil-ions for single ionization of helium by fast, heavy-ion impact

Helium single ionization by 3.6 MeV/u Ni24+ impact was explored in a kinematically complete experiment by combining a high-resolution recoil-ion momentum spectrometer with a novel 4π low-energy electron analyzer. More than 90% of the ''soft electrons'' (Ee> or ∼50 eV) are ejected in the forward direction in agreement with CTMC predictions. The electron longitudinal momentum is not balanced by the longitudinal momentum change of the projectile but mainly by the backwards recoiling He1+-ion. Energy losses of the 0.2 GeV projectiles as small as ΔEP/EP=3.4.10-7 are observable. (orig.)