Ejection angles of fast delta electrons from K-shell ionisation induced by energetic ions

The angular distribution of fast delta electrons from K-shell ionisation is discussed within the framework of the impact parameter Born approximation (SCA theory). Analytical expressions for the triply differential cross section are derived based on simplifying the peaking approximation. These expressions are easily evaluated and the structures in the momentum distributions of the ejected electrons are discussed. The most dominant feature appears to be the so-called binary ridge, the shape of which shows only a weak dependence on the impact parameter of the collision.