Saturation effects in highly charged ion interaction with thin carbon foils

Abstract

We present a set of experimental values for relative cross sections of Auger electron production in carbon foils for projectile charges QP ranging from 6 to 39 and fixed projectile velocity 19.2 atomic units. We deduce the 1s single and double ionisation cross sections and their relative variation with respect to the projectile charge. The cross section saturates for the largest projectile charges. However, the comparison of the experimental data with continuum distorted wave-eikonal initial state (CDW-EIS) and classical trajectory Monte Carlo (CTMC) calculations shows that this saturation effect is not well reproduced by the calculations. We suggest that the observed saturation effect in 1s-shell ionisation could be due to multiple electron effects not included in these models based on independent electron approximation. We have then simulated the backward electron emission yield γB taking into account this strong saturation effect for the 1s shell. We obtained a better agreement for both the emission yield γB and the stopping power. The electron emission simulation gives some insight on the relative contribution of valence and 1s-shell to saturation effects.