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 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 …

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 …

Helium is a prototype three-body system and has long been a model system for developing
quantum mechanics theory and computational methods. The fine-structure splitting in the …

We have measured the forbidden 2 S 1 3→ 2 P 1 1 transition at 887 nm in a quantum
degenerate gas of metastable He 4 atoms confined in an optical dipole trap. The determined …

Quantum electrodynamical (QED) calculations of ionization energies of the 1 snd D states
are performed for the helium atom. We reproduce the previously known relativistic and QED …

We have calculated ac polarizabilities of the 2 3 S and 2 1 S states of both He 4 and He 3 in
the range 318 nm to 2.5 μ m and determined the magic wavelengths at which these …

We report the frequency measurements of the 2 P 3→ 3 D 3 transitions in He 3, 4 at 588 nm
using an optical frequency comb stabilized laser system. The Doppler-free spectra of the 2 P …

We perform quantum-electrodynamic calculations of the ionization energy of the 1 s 3 d
states of the He 4 atom, including a complete evaluation of the m α 6 correction. We find a …

We present precise frequency measurement of the 2 S 0 1-3 D 2 1 two-photon transition in
He 4 at 1009 nm. The laser source at 1009 nm is stabilized on an optical frequency comb to …