New studies of the mechanism of electron emission at zero degrees in collisions of 100 keV protons with H-2 and He

Measurements of double differential cross sections for electron emission at zero degrees arising from collisions of 100 keV protons with H-2 and He ha ve been carried out. Calculations based on a continuum-distorted-wave eikon al-initial-state model have also been carried out and shown to provide a go od description of the measurements. In addition, classical-trajectory Monte Carlo calculations have been employed to illustrate the evolution of elect ron emission at different rimes during the collision. The present measureme nts, which use a well defined gas target, provide no evidence of the existe nce of a significant saddle-point ionization mechanism at the energy consid ered.