Convoy electrons associated with neutral ejectiles

Abstract

Convoy electrons are important in the understanding of the interaction processes of swift, heavy ions in matter, providing information about the influence of the projectile on the production and transport of electrons through solids. One crucial point of discussion is whether these convoy electrons are created in the bulk or only upon exit of the projectile from the solid. The observation of convoy electrons associated with neutral ejectiles can provide a stringent test to distinguish between bulk and surface models. Forward electron energy spectra in coincidence with the emergent charge states of H + and He + projectiles (100–400 keV/u) impinging upon thin carbon foils have been measured. Convoy electrons were observed associated with neutral as well as charged ejectiles. These results favour bulk models, although the observed yields for neutrals are up to a factor 18 smaller than for charged particles, which indicates that the formation of convoy electrons might occur in the last layers of the solid.