Wavelengths and fine structure of2s−2ptransitions in two- and three-electron ions

Abstract

We present an analysis of our recent experimental wavelengths for the $1s2s{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}-1s2p{}_{}{}^3{}_{}{}^{}P_{0,2}^{}{}_{}{}^{}$ transitions of ClXVI and compare the results with theory and other experiments for the HeI isoelectronic sequence. The limits of precision of wavelength measurements obtained using fast-ion-beam sources are detailed. We discuss the limited precision of present theory for the energies of bound states of the relativistic two-electron systems and show that higher-order quantum electrodynamic and relativistic corrections are needed to obtain agreement with our measurements. We present a similar comparison of experiment and theory for the resonance transitions $2s{}_{}{}^2{}_{}{}^{}S-2p{}_{}{}^2{}_{}{}^{}P$, of the LiI isoelectronic sequence and discuss recent results for systems of more electrons. We conclude that many useful tests of multielectron quantum electrodynamic and relativistic corrections can be made by existing and future measurements of wavelengths and fine structure in medium-$Z$ ions of a few electrons.