Interactions of Highly Charged Ions with C₆₀ and Surfaces

Abstract

Slow collisions between highly charged ions and many-electron targets, such as large atoms, molecules, clusters, or surfaces, usually lead to the transfer of several electrons from the complex target to the projectile. The efficient capture of target electrons is related to the relatively long (on an atomic time scale) interaction time of typically several femtoseconds and the strong Coulomb force of the highly charged projectile that acts like a vacuum cleaner for loosely bound target electrons while offering a large number of excited projectile states into which electrons can be captured. This chapter will cover part of the interesting physics involved in collisions with two particular types of complex targets: gaseous C₆₀ (as a representative for easily mass-selected carbon-cage molecules called “fullerenes”) and solid surfaces. The theoretical description of these collisions is presented as simply as possible, with a strong emphasis on the modeling of basic electronic interaction mechanisms. For C₆₀ targets, a variety of observables recently have been measured in laboratories around the world against which existing models can be scrutinized. While for C₆₀ targets modern coincidence experiments allow for the selection of distant projectile trajectories that do not result in the destruction of the target’s carbon cage, even in the most grazing collisions between highly charged ions and surfaces, close encounters cannot be avoided. This complicates the study of collisions with surfaces to the extent that the interaction mechanisms which dominate while the ion is close to (and possibly inside) a surface are not yet understood in full detail. These mechanisms are a matter of intense ongoing research to which the reader will be introduced in this chapter.