HIGHER-ORDER CONTRIBUTIONS TO IONIZATION PLUS EXCITATION CROSS-SECTIONS IN HIGH-ENERGY E-+HE AND H++HE SCATTERING

We have determined absolute cross sections for ionization-excitation o f He by energetic electron and proton projectiles. Using a semi-empiri cal analytic formula we- have been able to decompose our He+ (np) cros s section data in leading order terms which are proportional to Z(p)n for n = 2, 3 and 4. In particular we have found a strong Z(p)3 depende nce which appears to represent quantum interference effects. The set o f amplitude coefficients obtained here is universal for both our elect ron and proton cross section results from He+ (np) state with principa l quantum numbers n = 2 to 5.