Target dependence of binary encounter electron peak anomalies in collisions of partially stripped heavy ions with molecular hydrogen and noble gases

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Abstract
A systematic search was performed for the manifestation of quantum interference effects in the shape and angular distribution of the binary-encounter electron peak in collisions of partially stripped, or structured, heavy ions with noble gases and molecular hydrogen. The ionic species investigated were Cu5+,19+, I7+,23+, Au11+,29+ and U13+, all at the same nominal velocity equivalent to 0.6 MeV amu-1. Experimental double-differential cross sections for secondary electron emission in the binary encounter energy region are compared with a simple model based on the elastic scattering of quasi-free target electrons in the projectile field as well as with results of impulse approximation (IA) calculations. While these calculations provide a good qualitative overall description of the observed quantum effects for noble gas targets, this is not the case for H2 targets. An attempt was made to incorporate target molecular structure into the impulse approximation code by allowing the binary electron amplitudes from each of the hydrogen atoms, assumed to constitute the H2 molecule, to interfere. This approach, while demonstrating the strong influence of molecular orientation upon the intermediate energy region of the cross sections, did not meet with success, thereby indicating the necessity to consider the final-state interaction of the binary electron with the two protons of the residual H2+ or H22+ target.