Measurements of 2s S-2(1/2)-2p P-2(1/2,3/2) transition energies in lithiumlike heavy ions. II. Experimental results for Ag44+ and discussion along the isoelectronic series

Wavelengths of the fine structure transitions 2s S-2(1/2)-2p P-2(3/2) and 2 s S-2(1/2)-2p P-2(1/2) in lithiumlike Ag44+ have been measured using beam-f oil excitation and grazing incidence spectroscopy. The respective transitio n wavelengths of 40.829+/-0.004 Angstrom and of 124.685+/-0.009 Angstrom we re not measured before for this ion. The achieved precision of 70 ppm for t he 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 calcul ated two-photon exchange contributions to the transition energy. A summary of all published experimental data along the isoelectronic sequence for Z g reater than or equal to 24, including our recent results: for Ni25+ and Zn2 7+. is presented and compared with the best available calculations. [S1050- 2947(99)02703-1].