Measurement of theD-line doublet in high-Zhighly charged sodiumlike ions

Abstract

We report a direct observation of the $D$-line doublet of Na-like ions with $Z\ensuremath{\ge}72$. Spectra in the 1--9 nm spectral range are presented showing the widely split doublet for ${\text{Hf}}^{61+}$, ${\text{Ta}}^{62+}$, ${\text{W}}^{63+}$, and ${\text{Au}}^{68+}$. The ions were produced and confined in an electron-beam ion trap and observed with a flat-field grazing incidence spectrometer. The measured wavelengths agree well with the predictions of relativistic many-body perturbation theory with QED corrections. We also report the measured wavelengths for several transitions in Si-, Al-, and Mg-like ions of Hf, Ta, and W and in Mg-like Au.