Energy Loss and Charge Exchange of Highly Charged Ions in Carbon Nanomembranes


Energy Loss and Charge Exchange of Highly Charged Ions in Carbon Nanomembranes

Facsko, S.; Wilhelm, R. A.; Gruber, E.; Ritter, R.; Heller, R.; Aumayr, F.

During the interaction of highly charged ions with solids the ions potential energy, i.e. the stored ionization energy, is released via multiple charge exchanges on a fs time scale. Thus, HCIs reach charge equilibrium after passing only a few nanometers of the solid. The dependence of the charge state on the stopping force of the ions is therefore not accessible in irradiation experiments with bulk material. In order to investigate this pre-equilibrium regime films of just a few nanometers have to be used.
We examined the charge state and the energy loss of highly charged Xe ions after their passage through 1 nm thick carbon nanomembranes. Surprisingly, two distinct exit charge distributions were observed [1]. Part of the ions are passing the membrane with almost now charge loss, whereas the other part loose most of their charge. Apparently, the measured charge distribution reflects two different impact parameter regimes. Ions with trajectories far away of any C atom of the membrane can stabilize only few electrons and exit therefore in a high charge state, whereas ions with trajectories close to a C atom can capture enough electrons and exit the membrane in a low charge state. The different impact parameter regimes are also connected to different energy losses: ions with large impact parameters are practically not stopped, whereas ions in close collisions exhibit high stopping force which is strongly dependent on the incident charge state.
The charge distribution and energy loss of Xeq+ ions of different incident charge states up to q=30 will be presented and the implication for the formation of holes in these nanomembranes by the HCIs [2] will be discussed.

[1] R.A. Wilhelm, E. Gruber, R. Ritter, R. Heller, S. Facsko, F. Aumayr, Phys. Rev. Lett. 112, 153201 (2014).
[2] R. Ritter, R.A. Wilhelm, M. Stöger-Pollach, R. Heller, A. Mücklich, U. Werner, H. Vieker, A. Beyer, S. Facsko, A. Gölzhäuser, F. Aumayr, Appl. Phys. Lett. 102, 063112 (2013).

Keywords: highly charged ions; nano membranes; energy loss

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