Precision vacuum-ultraviolet wavelengths of Fe II measured by Fourier-transform and grating spectrometry

We have measured the wavelengths of 236 Fe ii lines between 150 and 200 nm, using Fourier-transform spectrometry. These measurements have been combined with those of 237 lines from 92.7 to 150 nm in high-resolution grating spectra. Ritz wavelengths for all 473 lines have been determined from energy-level values derived from ultraviolet, visible, and infrared Fourier-transform spectrometry and are recommended as wavelength standards with an uncertainty ranging from 0.009 to 0.07 pm (0.005–0.02 cm-1). Recent developments in calibrating the spectra from Ar ii line standards are discussed.