Fine structure of helium-like ions and determination of the fine structure constant

We report a calculation of the fine structure splitting in light helium-like atoms, which accounts for all quantum electrodynamical effects up to order \alpha^5 Ry. For the helium atom, we resolve the previously reported disagreement between theory and experiment and determine the fine structure constant with an accuracy of 31 ppb. The calculational results are extensively checked by comparison with the experimental data for different nuclear charges and by evaluation of the hydrogenic limit of individual corrections.Comment: 4 pages, 3 tables, with a typo in Eq. (9) correcte

Fine structure of helium and light helium-like ions

Calculational results are presented for the fine-structure splitting of the 2^3P state of helium and helium-like ions with the nuclear charge Z up to 10. Theoretical predictions are in agreement with the latest experimental results for the helium fine-structure intervals as well as with the most of the experimental data available for light helium-like ions. Comparing the theoretical value of the 2^3P_0-2^3P_1 interval in helium with the experimental result [T. Zelevinsky et al. Phys. Rev. Lett. 95, 203001 (2005)], we determine the value of the fine-structure constant \alpha with an accuracy of 31 parts per billion.Comment: proceedings of the PSAS2010 conference. One misprinted digit in Table I is correcte

Logarithmic two-loop corrections to the Lamb shift in hydrogen

Higher order $(\alpha/\pi)^2 (Z \alpha)^6$ logarithmic corrections to the hydrogen Lamb shift are calculated. The results obtained show the two-loop contribution has a very peculiar behavior, and significantly alter the theoretical predictions for low lying S-states.Comment: 14 pages, including 2 figures, submitted to Phys. Rev. A, updated with minor change

Relativistic corrections to the long range interaction between closed shell atoms

The complete $O(\alpha^2)$ correction to the long range interaction between neutral closed shell atoms is obtained, the relation to the asymptotic expansion of the known short range interaction at the atomic scale is presented and a general interaction potential which is valid in the whole range of the inter atomic distances is constructed.Comment: 9 pages, accepted for Phys. Rev.

Muonic hydrogen and the proton radius puzzle

The extremely precise extraction of the proton radius by Pohl et al. from the measured energy difference between the 2P and 2S states of muonic hydrogen disagrees significantly with that extracted from electronic hydrogen or elastic electron-proton scattering. This is the proton radius puzzle. The origins of the puzzle and the reasons for believing it to be very significant are explained. Various possible solutions of the puzzle are identified, and future work needed to resolve the puzzle is discussed.Comment: Minor modifications, some references added, to appear in Annu. Rev. Nucl. Part. Sci. Vol 63 (2013). 60 pages, 5 figures, 1 tabl