IMPULSE APPROXIMATION TREATMENT OF ELECTRON-ELECTRON EXCITATION AND IONIZATION IN ENERGETIC ION-ATOM COLLISIONS

The effect of electron-electron interactions between projectile and ta rget electrons observed in recent measurements of projectile K-shell e xcitation [T.J.M. Zouros et al., Phys. Rev. Lett. 62 (1989) 2261] and ionization [T.J.M. Zouros et al., Nucl. Instr. and Meth. B56/57 (1991) 107 and D.H. Lee et al., Phys. Rev. A46 (1992) 13741 using O' project ile Auger electron spectroscopy are analysed within the framework of t he impulse approximation (IA) [D. Brandt, Phys. Rev. A27 (1983) 1314]. The IA formulation is seen to give a good account of the threshold be havior of both ionization and excitation, while providing a remarkably simple intuitive picture of such electron-electron interactions in io n-atom collisions in general. Thus, the applicability of the IA treatm ent is extended to cover most known processes involving such interacti ons including resonance transfer excitation, binary encounter electron production, electron-electron excitation and ionization.