We perform ab initio QED calculations of energy levels for the n = 1 and n = 2 states of He-like ions with the nuclear charge in the range Z = 12-100. The complete set of two-electron QED corrections is evaluated to all orders in the parameter αZ. Uncalculated contributions to energy levels come through orders α 3 (αZ) 2 , α 2 (αZ) 7 , and higher. The calculation presented is the first treatment for excited states of He-like ions complete through order α 2 (αZ) 4 . A significant improvement in accuracy of theoretical predictions is achieved, especially in the high-Z region.

The ground-state hyperfine splitting values of high-Z hydrogenlike ions are calculated. The relativistic, nuclear, and QED corrections are taken into account. The nuclear magnetization distribution correction ͑the Bohr-Weisskopf effect͒ is evaluated within the single-particle model with the g S factor chosen to yield the observed nuclear moment. An additional contribution caused by the nuclear-spin-orbit interaction is included in the calculation of the Bohr-Weisskopf effect. It is found that the theoretical value of the wavelength of the transition between the hyperfine-splitting components in 165 Ho 66ϩ is in good agreement with experiment.

The relativistic nuclear recoil corrections to the energy levels of low-laying states of hydrogen-like and high Z lithium-like atoms in all orders in αZ are calculated. The calculations are carried out using the B-spline method for the Dirac equation. For low Z the results of the calculation are in good agreement with the αZ -expansion results. It is found that the nuclear recoil contribution, additional to the Salpeter's one, to the Lamb shift (n = 2) of hydrogen is −1.32(6) kHz. The total nuclear recoil correction to the energy of the (1s) 2 2p 1 2 − (1s) 2 2s transition in lithium-like uranium constitutes −0.07 eV and is largely made up of QED contributions.PACS number(s): 12.20.Ds, 31.30.Jv

A possibility for investigations of quantum electrodynamics (QED) in experiments on the hyperfine splitting in heavy ions is examined. It is found that QED effects can be probed on the level of a few percent in a specific difference of the hyperfine splitting values in hydrogenlike and lithiumlike bismuth. This could provide a test of QED in the strongest electric field available at present for experimental study.

The relativistic nuclear recoil, higher-order interelectronic-interaction, and screened QED corrections to the transition energies in Li-like ions are evaluated. The calculation of the relativistic recoil effect is performed to all orders in 1/Z. The interelectronic-interaction correction to the transition energies beyond the two-photon exchange level is evaluated to all orders in 1/Z within the Breit approximation. The evaluation is carried out employing the large-scale configurationinteraction Dirac-Fock-Sturm method. The rigorous calculation of the complete gauge invariant sets of the screened self-energy and vacuum-polarization diagrams is performed utilizing a local screening potential as the zeroth-order approximation. The theoretical predictions for the 2p j − 2s transition energies are compiled and compared with available experimental data in the range of the nuclear charge number Z = 10 − 60.

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Using a model methane-like chiral system, we theoretically demonstrate a possibility to access photoelectron circular dichroism (PECD) by a single experiment with two overlapping laser pulses of carrier frequencies ω and 2ω, which are linearly polarized in two mutually-orthogonal directions. Depending on the relative phase, the resulting electric field can be tailored to have two different rotational directions in the upper and lower hemispheres along the polarization of the ω-pulse. We predict a strong forward/backward asymmetry in the emission of photoelectrons from randomly oriented samples, which has an opposite sign in the upper and lower hemispheres. The predicted PECD effect is phase-and enantiomer-sensitive, providing new insight in this fascinating fundamental phenomenon. The effect can be optimized by varying relative intensities of the pulses. 33.20.Xx, 33.55.+b, 81.05.Xj In 1976, it was predicted theoretically that photoionization of chiral molecules is sensitive to the helicity of ionizing light [1]. The effect emerges already in the electric-dipole approximation and manifests itself as a forward/backward asymmetry in the emission of photoelectrons from randomly oriented chiral molecules in the gas phase. It took about 25 years to verify these theoretical predictions experimentally [2,3]. Later on, this enantiomer-and helicity-selective effect was termed as photoelectron circular dichroism (PECD) [4]. During the last decade, one-photon ionization of chiral molecules by circularly polarized radiation, and the emerging PECD effects, were studied in the numerous experimental and theoretical works (see, e.g., review articles [5][6][7]).Recently [8,9], a similar PECD effect has been observed in the multiphoton ionization of chiral molecules by circularly polarized laser pulses. Since then, extensive experimental studies provided many important details on the multiphoton PECD, like, e.g., on its dependence on the pulse intensity and ellipticity [10-12], on the enantiomeric excess of the target [13,14], or on the intermediate electronic states involved in different multiphoton ionization schemes [15,16]. In addition, an impact of the nuclear and electron dynamics during multiphoton ionization of chiral molecules have been demonstrated by pump-probe experiments [17][18][19][20]. Theoretical approaches to describe the multiphoton PECD range from time-independent perturbative ab-initio calculation of the two-photon absorption followed by one-photon ionization in hydrogenic continuum spectrum [21] to nonperturbative time-dependent methods [22,23].Employing overlapping bichromatic laser pulses is a particularly important example of coherent control schemes [24,25]. Here, interference between the nphoton route of one of the fields and the m-photon route of the other field can be controlled through the relative phase. According to the selection rules for multiphoton transitions in atoms, there are two control scenarios [24].If n and m are both odd or even numbers, the integral and differential cross section ca...

A systematic QED treatment of electron correlation is presented for ions along the lithium isoelectronic sequence. We start with the zeroth-order approximation that accounts for a part of the electron-electron interaction by a local model potential introduced into the Dirac equation. The residual electron correlation is treated by perturbation theory. Rigorous QED evaluation is presented for the first two terms of the perturbative expansion; the third-order contribution is calculated within the many-body perturbation theory. We report accurate numerical results for the electronic-structure part of the ionization potential for the n=2 states of all Li-like ions up to uranium.Comment: 20 pages, 5 figures, 6 table