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

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

Nonrelativistic QED approach to the bound-electron g factor

Within a systematic approach based on nonrelativistic quantum electrodynamics (NRQED), we derive the one-loop self-energy correction of order alpha (Zalpha)^4 to the bound-electron g factor. In combination with numerical data, this analytic result improves theoretical predictions for the self-energy correction for carbon and oxygen by an order of magnitude. Basing on one-loop calculations, we obtain the logarithmic two-loop contribution of order alpha^2 (Zalpha)^4 ln[(Zalpha)^-2] and the dominant part of the corresponding constant term. The results obtained improve the accuracy of the theoretical predictions for the 1S bound-electron g factor and influence the value of the electron mass determined from g factor measurements.Comment: 4 pages, RevTe

The off-resonant dielectronic recombination in a collision of an electron with a heavy hydrogen-like ion

The recombination of an electron with an (initially) hydrogen-like ion is investigated. The effect of the electron-electron interaction is treated rigorously to the first order in the parameter 1/Z and within the screening-potential approximation to higher orders in 1/Z, with Z being the nuclear charge number. The two-electron correction contains the dielectronic-recombination part, which contributes to the process not only under the resonance condition for the projectile energy but also in the regions far from resonances. The mechanism of the off-resonant dielectronic recombination is studied in detail.Comment: 9 pages, 2 tables, 3 figure

QED theory of the nuclear recoil with finite size

We investigate the modification of the transverse electromagnetic interaction between two point-like particles when one particle acquires a finite size. It is shown that the correct treatment of such interaction cannot be accomplished within the Breit approximation but should be addressed within the QED. The complete QED formula is derived for the finite-size nuclear recoil, exact in the coupling strength parameter $Z\,\alpha$. Numerical calculations are carried out for a wide range of $Z$ and verified against the $(Z\,\alpha)^5$ contribution. The comparison with the $Z\,\alpha$ expansion identifies the contribution of order $(Z\,\alpha)^6$, which is linear in the nuclear radius and numerically dominates over the lower-order $(Z\,\alpha)^5$ term.Comment: 5 pages, 1 figure, corrected description of $(Z \alpha)^5$ correctio