Observing forbidden radiative decay of highly charged ions in a compact Penning trap

We report observations of radiative decay from metastable states of highly charged ions captured in a newly-developed compact Penning trap. Ions of interest are created in the NIST electron beam ion trap (EBIT), extracted in an ion beamline, and captured in a compact Penning trap built in a novel unitary architecture to facilitate collection of photons emitted by stored ions. As an example, Ar$^{13+}$ ions are captured in one of the two fine structure levels forming the lowest lying states, allowing us to monitor the fluorescence (blue light) of the spin-flipping (M1) decay to the ground state. We present recent results from the newly deployed ion capture apparatus and briefly discuss previous in-EBIT experiments as well as an earlier study involving ion capture in an electrostatic Kingdon ion trap. Our results illustrate the potential of unitary Penning traps for a variety of studies,\footnote{J. N. Tan, \textit{et. al.}, ``Unitary Penning Traps,'' at this meeting (poster).} including experiments to produce hydrogenlike ions for spectroscopic tests of QED.\footnote{N.D. Guise,\textit{ et. al.}, ``Charge Exchange and spectroscopy with isolated highly charged ions,'' at this meeting.}