The current status of bound state quantum electrodynamics calculations of transition
energies for few-electron ions is reviewed. Evaluation of one and two body QED correction …

The technique of quantum electrodynamics (QED) calculations of energy levels in the
helium atom is reviewed. The calculations start with the solution of the Schrödinger equation …

We have derived the complete formula for the α 7 m contribution to energy levels of an
arbitrary triplet state of the helium atom, performed numerical calculations for the 2 3 S and 2 …

We critically examine the current status of theoretical calculations of the energies, the fine
structure, and the isotope shift of the lowest-lying states of helium, searching for unresolved …

In a recent breakthrough in first-principles calculations of two-electron systems, Patkóś,
Yerokhin, and Pachucki [Phys. Rev. A 103, 042809 (2021) PLRAAN 2469-9926 …

The 2 S 3–2 P 3 transition of He 4 was measured by comb-linked laser spectroscopy using a
transverse-cooled atomic beam. The centroid frequency was determined to be 276 736 495 …

The very high precision of current measurements and theory predictions of spectral lines in
few-electron atoms allows us to efficiently probe the existence of exotic forces between …

Helium (He) is the ideal atom to perform tests of ab initio calculations in two-electron
systems that consider all known effects, including quantum-electrodynamics and nuclear …

Improvements in both theory and frequency metrology of few-electron systems such as
hydrogen and helium have enabled increasingly sensitive tests of quantum …

With this work we start a project calculating the QED contribution of order α 7 m to the 2 P 3–
2 S 3 transition energy in helium, aiming for an accurate determination of the nuclear charge …