Measurements of2s2S1/2−2p2P1/2,3/2transition energies in lithiumlike heavy ions. II. Experimental results forAg44+and discussion along the isoelectronic series

Abstract

Wavelengths of the fine structure transitions $2s{}^{2}{S}_{1/2}\ensuremath{-}2p{}^{2}{P}_{3/2}$ and $2s{}^{2}{S}_{1/2}\ensuremath{-}2p{}^{2}{P}_{1/2}$ in lithiumlike ${\mathrm{Ag}}^{44+}$ have been measured using beam-foil excitation and grazing incidence spectroscopy. The respective transition wavelengths of 40.829\ifmmode\pm\else\textpm\fi{}0.004 \AA{} and of 124.685\ifmmode\pm\else\textpm\fi{}0.009 \AA{} were not measured before for this ion. The achieved precision of 70 ppm for the 1/2-1/2 transition allows for a 0.2% QED test which sets a new benchmark in the medium Z range. Our experimental uncertainty is smaller than calculated two-photon exchange contributions to the transition energy. A summary of all published experimental data along the isoelectronic sequence for $Zg~$24, including our recent results for ${\mathrm{Ni}}^{25+}$ and ${\mathrm{Zn}}^{27+},$ is presented and compared with the best available calculations.