An all-order procedure is used to determine the energies of the n= 1 and n= 2 states of
heliumlike ions with nuclear charges in the range Z= 3–100. The Coulomb energies and …

Transition frequencies and fine-structure splittings of the 2 S 1 3→ 2 P 3 J transitions in
helium-like C 4+ 12 were measured by collinear laser spectroscopy on a 1-ppb level …

A rigorous quantum electrodynamical calculation is presented for energy levels of the 1 1 S,
2 1 S, 2 3 S, 2 1 P 1, and 2 3 P 0, 1, 2 states of helium-like ions with the nuclear charge Z …

Essentially exact calculations of the nonrelativistic wave functions and energies of helium
are reviewed, together with the lowest-order relativistic corrections. The results are extended …

In a proof-of-principle experiment, we demonstrate high-resolution resonant laser excitation
in the soft x-ray region at 48.6 eV of the 2 S 1/2 2 to 2 P 1/2 2 transition of Li-like Fe 23+ ions …

High-precision laser-resonance measurements accurate to±0.5 MHz or better are reported
for transitions among the 1s2s 3 S 1–1s2p 3 PJ hyperfine manifolds for each of J= 0, 1, and …

We report a calculation of the fine-structure splitting in light heliumlike atoms, which
accounts for all quantum electrodynamical effects up to order α 5 Ry. For the helium atom …

Standard perturbation theory in quantum mechanics is employed to calculate the mass shifts
of 2 S 0 1− 2 S 1 3 and 2 S 1 3− 2 PJ 3 transitions in Be 2+ 7, 9, 10, 11, 12, 14 ions. These …

A reformulation of the external potential Bethe-Salpeter formalism is developed for two-
electron atoms. QED and relativistic corrections to energy levels of order α 7 mc 2 ln α are …

A systematic calculation of the hyperfine structure of 2 3 P levels of heliumlike ions is
presented. Reduced matrix elements of the magnetic-dipole hyperfine operator between …