0 degrees Binary encounter electron production in 30-MeV O-q++H-2, He, O-2, Ne, and Ar collisions

Double-differential cross sections (DDCS's) for the production of binary encounter electrons (BEE's) were measured for collisions of 30-MeV O-q+ projectiles with H-2, He, O-2, Ne, and Ar targets with q=4-8 and an electron ejection angle of theta=0 degrees with respect to the beam direction. Particular interest focused on (a) the evaluation of the contributions of the different electron subshells of the multielectron targets, O-2, Ne, and Ar; (b) the study of the well-known enhancement of the BEE DDCS's with decreasing projectile charge-state q; here this dependence was tested for higher collision energies and new targets; (c) the study of the dependence of the BEE peak energy on the particular target and projectile charge state. Results were analyzed in terms of the impulse approximation, in which target electrons in the projectile frame undergo 180 degrees elastic scattering in the field of the projectile ion. The electron scattering calculations were performed in a partial-wave treatment using the Hartree-Fock model. Good agreement with the data was found for the H-2 and He targets, while for the multielectron targets O-2, Ne, and Ar only electrons whose velocity was lower than the projectile velocity needed to be included for good agreement. All measured BEE DDCS's were found to increase with decreasing projectile charge state, in agreement with other recent BEE results. The BEE peak energies were found to be independent of the projectile charge state for all targets utilized.