The Interatomic Coulombic Decay in ion neutralization at surfaces

Abstract

The interaction of highly charged ions with surfaces is accompanied by electron transfer, electronic excitation and decay processes, as well as the emission of multiple particles such as elec- trons, photons and surface atoms [1, 2]. In or- der to disentangle the complexity of charge ex- change and energy dissipation channels during ion–surface collisions, we apply a coincidence de- tection of ions after the interaction with a free- standing two-dimensional material and electrons emitted from the material. With this multi– particle spectroscopy technique, we can show that the ion charge exchange [3] and the elec- tron emission [4] depend both on the internuclear distance during transmission of the ion through a freestanding layer of graphene. Fig. 1 shows the measured charge exchange between highly charged Xe ions and single layer (SLG), bilayer (BLG), and trilayer graphene (TLG) as func- tion of scattering angle. A strong angle depen- dence can be observed for SLG which indicates a strong internuclear distance dependence. At thicker samples this dependence washes out due to multiple scattering as well as an overall in- creasing interaction time. For initially slower ions the angular dependence appears also flat for SLG due to a long interaction time compared to the ICD lifetime. Modeling of trajectory–dependent charge ex- change based on these findings [5] and subsequent quantitative comparison to experimental data re- veals that the ion energy release depends strongly on the internuclear distance, closely resembling the prediction from Interatomic Coulombic De- ∗E-mail: wilhelm@iap.tuwien.ac.at cay. In this presentation, I will discuss recent ex- perimental findings on the ion interaction with surfaces and 2D materials with multiple–particle spectroscopy. In particular I will show energy– and angle–resolved data for both the ion scat- tering as well as the emission pattern of elec- trons from surfaces, consistent with expectations from the wider framework of interatomic Auger- Meitner type energy release channels.