2017ApJ...850...57B

We measured the L-shell emission spectrum of Fe XVII in a low-density, low-gradient magnetically confined laboratory plasma that contains predominately C, O, Fe, and Ni as trace elements and found excellent agreement with the relative spectral emission obtained in solar and astrophysical observations. However, we obtained spectra that appear to have an usually large 1s²2s²2p_1/2⁵3d_3/2→1s²2s²2p⁶ Fe XVII resonance transition, which is commonly labeled 3C, from hot plasmas that also contain fluorine. The wavelength of the Lyα feature of F IX is coincident with the wavelength of the Fe XVII line 3C within one part in 538, and its flux, therefore, enhances the Fe XVII resonance line. Moreover, the resonance and forbidden lines of F VIII are close to the 3s→2p transitions in Fe XVII and may further alter the inferred apparent Fe XVII line ratios, particularly in spectrometers with moderate spectral resolution. The enhanced emission of line 3C can thus serve as a new spectral diagnostic for the detection of fluorine in astrophysical plasmas.