  Motivated by possible atomic origins of the unidentified emission line
detected at 3.55 keV to 3.57 keV in a stacked spectrum of galaxy clusters
(Bulbul et al. 2014), an electron beam ion trap (EBIT) was used to investigate
the resonant dielectronic recombination (DR) process in highly-charged argon
ions as a possible contributor to the emission feature. The He-like Ar
DR-induced transition 1s$^2$2l - 1s2l3l$^\prime$ was suggested to produce a
3.62 keV photon (Bulbul et al. 2014) near the unidentified line at 3.57 keV and
was the starting point of our investigation. The collisional-radiative model
NOMAD was used to create synthetic spectra for comparison with both our EBIT
measurements and with spectra produced with the AtomDB database/Astrophysical
Plasma Emission Code (APEC) used in the Bulbul et al. (2014) work. Excellent
agreement was found between the NOMAD and EBIT spectra, providing a high level
of confidence in the atomic data used. Comparison of the NOMAD and APEC spectra
revealed a number of missing features in the AtomDB database near the
unidentified line. At an electron temperature of $T_e$ = 1.72 keV, the
inclusion of the missing lines in AtomDB increases the total flux in the 3.5
keV to 3.66 keV energy band by a factor of 2. While important, this extra
emission is not enough to explain the unidentified line found in the galaxy
cluster spectra.
