Spectroscopy of highly charged Rydberg ions made by dielectronic recombination in few-electron Ar*

Rydberg Highly Charged Ions (RyHCI) are interesting systems to study as they provide excellent test beds for precision tests of quantum electrodynamics and precision X-ray wavelength standards. Moreover, certain high angular momentum states are considered to be potentially useful for measuring fundamental constants. Dielectronic Recombination (DR) is a significant process that results in the production of Rydberg states. We present X-ray spectra as a function of the electron beam energy that show the signatures of different processes populating electronic levels including DR. Measurements were done at the Electron Beam Ion Trap (EBIT) facility at the National Institute of Standards and Technology using an X-ray transition-edge sensor micro calorimeter. The Flexible Atomic Code (FAC) was used to identify the X-ray features related to the atomic processes involved.