Strong dependence of zero degree binary encounter electron production on the initial and final charge state

Doubly differential cross sections d2 sigma /dEed Omega e and fractional probabilities for binary encounter (BE) electron emission at 0' electron emission angle as a function of initial (qi) and final (qf) projectile charge state have been measured for 0.53 MeV u-1 Fqi on H2. The data confirm the surprising decrease of the partial cross section with increasing charge state of the incoming projectile qi reported by Richard et al. (1990). The authors show by coincident electron projectile detection that the pure ionization channel qi=qf strongly dominates the differential cross section at theta e=0' and projectile capture and loss channels are of negligible importance. In view of a calculation by Olson et al. (1990) they conclude from their data that 0' BE electron emission depends strongly on the shape of the screened projectile potential varying with qi.