Search for a double-collision mechanism as a possible interpretation for ionization by low-energy light-ion impact

Abstract

In a previous work we proposed, in the frame of the binary-encounter approximation (BEA) of the inner-shell atomic ionization by ion bombardment, a correction to the ion energy in order to account for the Coulomb repulsion by the atomic nucleus. Such corrected cross-section values numerically coincide with those of the PWBA model, but, as a consequence of the correction, we obtain a much higher-energy ionization threshold than the binding energy, which has no experimental evidence. In the present work we show that ionization below such a threshold can be explained by a double-collision mechanism which involves intermediate electron states and can directly be derived from the impulsive nature of the binary-collision model. Calculations have been performed by supposing a statistical independence between these two collisions. Relativistic corrections have not been taken into account. We have obtained a remarkable agreement between the curves corresponding to single- and double-collision classical processes, since they match at the bombarding threshold ion energy.