Scaling of cross sections in ion-atom collisions

Differential electron emission at 15{degrees} is investigated for 50-500 keV/amu hydrogen impacting on He and H targets. From hydrogen particles (H, H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}) ratios of cross sections relative to proton impact data, it is shown how bound projectile electrons influence the differential electron emission and where different ionization mechanisms are important. It is demonstrated that the H{sub 2}{sup +} and H{sub 3}{sup +} molecular ions interact as though they are composed of independent nuclei with the appropriate number of bound electrons, the electronic structure of the components appearing to be unimportant.