COULOMB PATH INTERFERENCE IN LOW-ENERGY HE+ + HE COLLISIONS

Coulomb "path" interference results from the existence of two trajectories, indistinguishable with respect to laboratory energy and emission angle, along which ejected autoionizing electrons may be scattered by the attractive Coulomb potential of the slowly receding spectator ion. Experimental evidence for this new phenomenon exists in the uncharacterestically rapid angular dependence of the postcollision broadened lineshape of the He target 2s21S autoionizing state measured near 0-degrees following 10 keV He+ + He collisions. We present a semiclassical model for this effect in which we account for the path dependence of the amplitude of the ejected electron following decay of the autoionizing state. Calculated model lineshape, which include contributions from adjacent overlapping resonances, are found to be in excellent agreement with the angular dependence observed in the data. Similar interference structure is observed in the calculated lineshape for a single isolated 2s21S resonance.