We have made the first interferomeric measurements of the wavelengths of the important ultraviolet diagnostic lines in the spectra \ion{ C}{ 4} near 155 nm and \ion{ Si}{ 4} near 139 nm with a vacuum ultraviolet Fourier transform spectrometer and high-current discharge sources. The wavelength uncertainties were reduced by one order of magnitude for the \ion{ C}{ 4} lines and by two orders of magnitude for the \ion{ Si}{ 4} lines. Our measurements also provide accurate wavelengths for resonance transitions in \ion{ Al}{ 3}, \ion{ Al}{ 2}, and \ion{ Si}{ 2}.
Categories: astro-ph