Corrections of order alpha 2(Z alpha )5 to the hyperfine splitting and the Lamb shift

Precision Spectroscopy of the Pionic Helium-4

The transition frequency of (n,ℓ)=(17,16)→(16,15) in pionic helium-4 is calculated to an accuracy of 4 ppb (parts per billion), including relativistic and quantum electrodynamic corrections up to O(R_{∞}α^{5}). Our calculations significantly improve the recent theoretical values [Hori et al., Phys. Rev. A 89, 042515 (2014)PLRAAN1050-294710.1103/PhysRevA.89.042515]. In addition, collisional effects between pionic helium and target helium on transition frequencies are estimated. Once measurements reach the ppb level, our Letter will improve the value of the π^{-} mass by 2-3 orders of magnitude.

Two-Loop Binding Corrections to the Electron Gyromagnetic Factor

We compute corrections to the gyromagnetic factor of an electron bound in a hydrogenlike ion at order α^{2}(Zα)^{5}. This result removes a major uncertainty in predictions for silicon and carbon ions, used to determine the atomic mass of the electron.

Nonperturbative calculation of the two-loop lamb shift in Li-like ions

A calculation valid to all orders in the nuclear-strength parameter is presented for the two-loop Lamb shift, notably for the two-loop self-energy correction, to the 2p-2s transition energies in heavy Li-like ions. The calculation removes the largest theoretical uncertainty for these transitions and yields the first experimental identification of two-loop QED effects in the region of the strong binding field.

Giant lamb shift in photonic crystals

We obtain a general result for the Lamb shift of excited states of multilevel atoms in inhomogeneous electromagnetic structures and apply it to study atomic hydrogen in inverse-opal photonic crystals. We find that the photonic-crystal environment can lead to very large values of the Lamb shift, as compared to the case of vacuum. We also suggest that the position-dependent Lamb shift should extend from a single level to a miniband for an assembly of atoms with random distribution in space, similar to the velocity-dependent Doppler effect in atomic/molecular gases.

Two-loop self-energy correction in high-Z hydrogenlike ions

A complete evaluation of the two-loop self-energy diagrams to all orders in Zalpha is presented for the ground state of H-like ions with Z > or =40.

Asymmetry of the natural line profile for the hydrogen atom

The asymmetry of the natural line profile for transitions in hydrogenlike atoms is evaluated within a QED framework. For the Lyman- alpha 1s-2p absorption transition in neutral hydrogen this asymmetry results in an additional energy shift of 2.929 856 Hz. For the 2s(1/2)-2p(3/2) transition it amounts to -1.512 674 Hz. As a new feature this correction turns out to be process dependent. The quoted numbers refer to the Compton-scattering process.

Order alpha(7)ln(1/alpha) contribution to positronium hyperfine splitting

The logarithmically enhanced alpha(7)ln(1/alpha) contribution to the hyperfine splitting of the positronium ground-state energy levels is calculated in the framework of dimensionally regularized nonrelativistic quantum electrodynamics. The correction is negative and amounts to about 1/3 of the leading logarithmic alpha(7)ln (2)(1/alpha) one. The discrepancy between the experimental measurements and the theoretical prediction is reduced.

Three-loop slope of the dirac form factor and the 1S lamb shift in hydrogen

The last unknown contribution to hydrogen energy levels at order malpha(7), due to the slope of the Dirac form factor at three loops, is evaluated in a closed analytical form. The resulting shift of the hydrogen nS energy level is found to be 3.016/n(3) kHz. Using the QED calculations of the 1S Lamb shift, we extract a precise value of the proton charge radius r(p) = 0.883+/-0.014 fm.