  We present the first high-resolution laboratory spectra of X-ray emission
following L-shell charge exchange between nickel ions and neutral H2 and He. We
employ the commonly used charge exchange models found in XSPEC and SPEX, ACX
and SPEX-CX, to simulate our experimental results. We show that significant
differences between data and models exist in both line energies and strengths.
In particular, we find that configuration mixing may play an important role in
generating lines from core-excited states, and may be improperly treated in
models. Our results indicate that if applied to astrophysical data, these
models may lead to incorrect assumptions of the physical and chemical
parameters of the region of interest.
