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J. Schwestka, R. Wilhelm, E. Gruber, R. Heller, R. Kozubek, M. Schleberger, S. Facsko, F. Aumayr:
"The role of radiative de-excitation in the neutralization process of highly charged ions interacting with a single layer of graphene";
Nuclear Instruments & Methods in Physics Research Section B, 422 (2018), 63 - 67.

X-ray emission of slow (< 1 a.u.) highly charged Argon and Xenon ions is measured for transmission through a
freestanding single layer of graphene. To discriminate against X-ray emission originating from the graphene's
support grid a coincidence technique is used. X-ray emission of 75 keV Ar17+ and Ar18+ ions with either one or
two K-shell vacancies is recorded. Using a windowless Bruker XFlash detector allows us to measure additionally
Ar KLL and KLM Auger electrons and determine the branching ratio of radiative vs. non-radiative decay of Ar Kshell
holes. Furthermore, X-ray spectra for 100 keV Xe22+-Xe35+ ions are compared, showing a broad M-line
peak for all cases, where M-shell vacancies are present. All these peaks are accompanied by emission lines at still
higher energies indicating the presence of a hollow atom during X-ray decay. We report a linear shift of the main
M-line peak to higher energies for increasing incident charge state, i.e. increasing number of M-shell holes.

Slow highly charged ions Graphene X-ray emission