Diffraction effects in the production of binary encounter electrons emitted in collisions of heavy ions with He and H2 targets

Relative double differential cross sections for electron emission in collisions of Iq+ and Xeq+ projectile ions incidence on H2 and He targets are presented for observation angles of 0 degree to 60 degree with respect to the beam. The measurements were performed over a wide range of projectile velocities (0.6 to 3.6 MeV/amu) and charge states (q=7 to 23). As the velocity or charge state of the projectile are decreased, drastic changes in the behavior of the binary encounter peak can be observed. These effects can be attributed to diffraction of the target electrons by the non-Coulomb potential of the clothed projectile ion. A theoretical treatment of the double differential cross sections has been developed where the binary encounter electrons are treated within the impulse approximation as the elastic scattering of quasi-free target electrons by the screened potential of the projectile ion