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R. Wilhelm:
"Highly Charged Ion Interaction with Surfaces and 2D-Materials";
Vortrag: Seminar Institut für Allgemeine Physik (IAP), TU Wien; 17.10.2017.

The impact of highly charged ions onto a solid surface gives rise to processes like charge exchange, ion stopping, formation of electronic excitations at the surface, scattering and sputtering. Subsequently the large amount of deposited energy (up to some 10keV) can lead to the formation of individual nanostructures at the surface ranging from pits to craters and even to hillocks depending on the material's response to the ion impact [1]. To study the energy deposition and it's time dependence experimentally we recently used freestanding two-dimensional materials (e.g. graphene) as a target. By adjusting the ion's kinetic energy it's interaction time with the 2D-solid can be controlled. Spectroscopic measurement of the ion after transmission allows the observation of a rapid charge capture and deexcitation process [2]. At the same time the ion experiences a large charge state dependent stopping force. In a joint theoretical and experimental effort ab-initio atomic and molecular structure calculations as well as time-dependent density functional theory simulations give insight into the charge exchange and deexcitation sequence upon impact of a highly charged ion on a solid surface [2,3]. Our study shows that highly charged ions are well suited to investigate material properties under extreme conditions on a femtosecond time scale.
[1] R. A. Wilhelm, A. S. El-Said et al., Prog. Surf. Sci. 90, 377 (2015).
[2] E. Gruber, R. A. Wilhelm et al., Nat. Commun. 7, 13948 (2016).
[3] R. A. Wilhelm, E. Gruber, J. Schwestka et al., Phys. Rev. Lett. 119, 103401 (2017).