BINARY ENCOUNTER PEAKS FOR 0-DEGREES ELECTRONS IN COLLISIONS BETWEEN 2 MEV/AMU SIQ+ AND HE

Binary encounter electrons originating from collisions between 56 MeV Si(q+) and He have been measured at zero degrees with respect to the beam direction. The dependence of the binary-encounter peak on the projectile charge state q = 6, 12, 13 and 14 (fully stripped Si) was studied. As earlier observed by Richard et al. (J. Phys. B 23 (1990) L213) using fluorine ions, we found that the binary-encounter electron production increased for decreasing charge state. This dependence which reflects the importance of outer screening has recently been treated in several theoretical papers and the present results are compared to estimates by K. Taulbjerg (private communication).