In Search of Collective Electron Emission from Heavy Ion Solid Collisions

The response of the electron plasma of a solid to an energetic (~ Mev/N), penetrating, charged particle manifests itself in electron density fluctuations behind the projectile. The potential o corresponding to these charge density fluctuations is the Wake potential.1 It can be characterized by the charge Zp and the velocity vp of the penetrating projectile and by the plasma properties of the solid (plasma frequency wp). The perturbation of the electron density2 propagates conically with a velocity vs through the solid under the Mach-relationship ϑem = arc cos (vs/vp) where ϑ is the angle between \( {\vec v_p} \) and \( {\vec v_s} \). It has been shown that this may lead to a preferential electron emission from a solid in the direction of the Mach-angle ϑem 2,3.