Zero-degree binary encounter electrons in fast collisions of highly charged F and O ions with H2 targets

Doubly differential cross sections (DDCS) for binary encounter electrons (BEe) produced by 0.5-2 MeV/u highly-charged F and O ions in collisions with H2 gas targets have been studied at 0 with respect to the ion beam direction. The measured DDCS of the broad binary encounter peak was well described by a simple impulse approximation (IA) treatment for bare ions, and was demonstrated to provide in situ detection efficiency of the electron spectrometer. The projectile energy dependence of the BEe production for nonbare (clothed) projectiles is found to follow a scaled IA prediction, in which a BEe enhancement is consistently exhibited for the collision energy range studied. (orig.)