Measurements and calculations of 2s−2p transitions in neonlike germanium: Achieving agreement at the 10−4 level

Abstract

Calculations that achieve spectroscopic accuracy, i.e., at the level of ${10}^{\ensuremath{-}4}$ or better, are rare and typically restricted to few-electron systems. Here we present high-resolution grating spectrometer measurements of 11 $2{s}_{1/2}\text{\ensuremath{-}}2{p}_{3/2}$ transitions in neonlike ${\mathrm{Ge}}^{22+}$ that distinguish between two different implementations of the many-body perturbation theory (MBPT) method, including our own. The measurements show that our implementation of the MBPT method consistently achieves spectroscopic accuracy at the ${10}^{\ensuremath{-}4}$ level for all of the measured lines. Moreover, our calculations improve the ${10}^{\ensuremath{-}3}$ accuracy of prior MBPT calculations by an order of magnitude and allow us to make greatly improved predictions of the location of potential photopumped lines in ${\mathrm{Ge}}^{22+}$. The measurements also improve on previous measurements of $2{s}_{1/2}\text{\ensuremath{-}}2{p}_{3/2}$ transitions in fluorinelike ${\mathrm{Ge}}^{23+}$ and oxygenlike ${\mathrm{Ge}}^{24+}$. Measurements of $n=2\phantom{\rule{4.pt}{0ex}}\text{to}\phantom{\rule{4.pt}{0ex}}n=3$ transitions in ${\mathrm{Al}}^{7+}$, ${\mathrm{Al}}^{8+}$, and ${\mathrm{Al}}^{9+}$ are used to support our measurement accuracy at the ${10}^{\ensuremath{-}5}$ level.