Transition energies of theDlines in Na-like ions

Abstract

The NIST electron beam ion trap (EBIT) was used to measure the ${D}_{1}$(3$s$-3${p}_{1/2}$) and ${D}_{2}$(3$s$-3${p}_{3/2}$) transitions in Na-like ions of xenon, barium, samarium, gadolinium, dysprosium, erbium, tungsten, platinum, and bismuth. The wavelengths are in the range 3--12 nm. Relativistic many-body perturbation theory calculations were carried out for the ${D}_{1}$ and ${D}_{2}$ lines for every element in the isoelectronic sequence from argon ($Z$ $=$ 18) to uranium ($Z$ $=$ 92), taking into account some higher-order terms in the quantum electrodynamics (QED) expansion. Uncertainties in the calculated values were carefully assessed by considering the uncertainties in the various contributions to the total calculated transition energies. We conclude that at the current level of accuracy, the calculated values can be taken to reliably represent the isoelectronic sequence from $Z$ $=$ 18 to 92. The agreement of theory and experiment for the ${D}_{1}$ line of bismuth ($Z$ $=$ 83) provides a test of QED at the level of 0.4$%$. Our results are also sensitive to retardation effects due to the finite speed of light and to variations in the assumed nuclear size.