High-resolution Charge Exchange Spectra with L-shell Nickel Show Striking Differences from Models

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.