Response of insulator surfaces to slow highly charged ions

The interaction of slow highly charged ions (HCI) with solid surfaces results in the formation of "hollow atoms", an exotic atomic state far from equilibrium. Whereas electronic transitions, which eventually restore the equilibrium could largely be identified for metal surfaces in experimental and theoretical studies during the last decade, similar processes at insulator surfaces are much less understood. The main differences as compared to HCI - metal interactions are (i) the different dielectric response of insulating surfaces (modified image charge acceleration, reduced hole mobility, etc.), (ii) local charging-up of the surface (leading to a partial repulsion of the projectile by positive hole charges on the surface), and (iii) the wide electronic band gap (altering transfer, excitation and emission of electrons). In order to study the response of an insulator surface to the strong perturbation introduced by a slowly approaching highly charged ion, specifically designed experiments will be carried out at TU Wien (with moderately charged HCI in charge states q < 20), and at Max Planck Institute of Nuclear Physics in Heidelberg/Germany for ions in much higher charge states q = 60). In particular, we will investigate electron emission, image charge attraction and electronic excitation of different insulator target surfaces. Accompanying simulations at the Institute for Theoretical Physics TU Wien will support the interpretation of the obtained experimental results.

The interaction of slow highly charged ions (HCI) with solid surfaces results in the formation of "hollow atoms", an exotic atomic state far from equilibrium. Whereas electronic transitions, which eventually restore the equilibrium could largely be identified for metal surfaces in experimental and theoretical studies during the last decade, similar processes at insulator surfaces are much less understood. The main differences as compared to HCI - metal interactions are 1. the different dielectric response of insulating surfaces (modified image charge acceleration, reduced hole mobility, etc.), 2. local charging-up of the surface (leading to a partial repulsion of the projectile by positive hole charges on the surface), and 3. the wide electronic band gap (altering transfer, excitation and emission of electrons). In order to study the response of an insulator surface to the strong perturbation introduced by a slowly approaching highly charged ion, specifically designed experiments will be carried out at TU Wien (with moderately charged HCI in charge states q < 20), and at Max Planck Institute of Nuclear Physics in Heidelberg/Germany for ions in much higher charge states q = 60). In particular, we will investigate electron emission, image charge attraction and electronic excitation of different insulator target surfaces. Accompanying simulations at the Institute for Theoretical Physics TU Wien will support the interpretation of the obtained experimental results.