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Abstract

In this work, a cryogenic electron beam ion trap (EBIT) for charge breeding of rare, short-lived isotopes at the ARIEL facility at TRIUMF was designed and assembled for future investigations of astrophysical processes. It was characterized at a maximum electron-beam current of 1 A. Furthermore, charge-exchange (CX) processes, which are relevant for the interface between hot plasmas and cold gases in astrophysical environments, were extensively studied. In these experiments, hydrogen-like and bare sulfur, argon, and oxygen ions capturing electrons from various neutral gas targets into highly-excited states with subsequent radiative relaxation via emission of X-rays were investigated. Thereby, a possible explanation for the recently observed emission line at 3.5 keV in galaxy clusters, with a proposed origin in the decay of sterile neutrinos, was given, in the form of CX induced K-shell emission from hydrogen-like sulfur. Additionally, measurements of extreme-ultraviolet L-shell transitions following CX into highly ionized oxygen in the range between 8 nm and 20 nm, utilizing a grating spectrometer, is presented. The results are compared with different CX models, mainly based on the multichannel Landau-Zener approach. Significant discrepancies between various experiments and models, as well as the models among each other, were ascertained and are extensively discussed.