arXiv subjects

V. A. Yerokhin

Publications and source records attributed to V. A. Yerokhin.

At least 91 records · Page 5Linked to original sources

arXiv2009

Reexamination of helium fine structure

In order to explain discrepancies between theoretical predictions and experimental data for the helium fine structure, we check and recalculate all theoretical contributions up to orders mα^7 and m^2/Mα^6. The previous result for the mα^7 correction is improved by a much more accurate calculation of relativistic corrections to the Bethe logarithm. The theoretical values of the 2^3P_0-2^3P_1 and 2^3P_1-2^3P_2 fine structure intervals in helium are, correspondingly, ν_{01} = 29616946.2(1.6) kHz and ν_{12} = 2291177.3(1.6) kHz, with the uncertanties being due to higher-order effects. For the small interval ν_{12}, the theoretical value agrees with the experimental data, whereas for the large interval ν_{01}, a discrepancy of about 3 standard deviations is present.

physics.atom-ph↗

arXiv2008

Hyperfine structure of Li and Be^+

A large-scale relativistic configuration-interaction (CI) calculation is performed for the magnetic-dipole and the electric-quadrupole hyperfine structure splitting in ^{7,6}Li and ^9Be^+. Numerical results for the 2^2S, 3^2S, 2^2P_{1/2}, and 2^2P_{3/2} states are reported. The CI calculation based on the Dirac-Coulomb-Breit Hamiltonian is supplemented with separate treatments of the QED, nuclear-magnetization distribution, recoil, and negative-continuum effects.

physics.atom-ph↗

arXiv2008

Electron self-energy in the presence of magnetic field: hyperfine splitting and g factor

A high-precision numerical calculation is reported for the self-energy correction to the hyperfine splitting and to the bound-electron g factor in hydrogenlike ions with low nuclear charge numbers. The binding nuclear Coulomb field is treated to all orders, and the nonperturbative remainder beyond the known $Zα$-expansion coefficients is determined. For the $^3{\rm He}^+$ ion, the nonperturbative remainder yields a contribution of -450 Hz to the normalized difference of the 1S and 2S hyperfine-structure intervals, to be compared with the experimental uncertainty of 71 Hz and with the theoretical error of 50 Hz due to other contributions. In the case of the g factor, the calculation provides the most stringent test of equivalence of the perturbative and nonperturbative approaches reported so far in the bound-state QED calculations.

physics.atom-ph↗

arXiv2008

Two-loop QED corrections with closed fermion loops

We report a calculation of all two-loop QED corrections with closed fermion loops for the n=1 and n=2 states of H-like ions and for a wide range of the nuclear charge numbers Z=1-100. The calculation is performed to all orders in the binding-strength parameter (Z α), with the exception that in a few cases the free-loop approximation is employed in the treatment of the fermion loops. Detailed comparison is made with previous (Z α)-expansion calculations and the higher-order remainder term to order α^2 (Z α)^6 is identified.

physics.atom-ph↗

arXiv2008

Hyperfine structure of S states in Li and Be^+

A large-scale configuration-interaction (CI) calculation is reported for the hyperfine splitting of the 2^2S and 3^2S states of ^7Li and ^9Be^+. The CI calculation based on the Dirac-Coulomb-Breit Hamiltonian is supplemented with a separate treatment of the QED, nuclear-size, nuclear-magnetization distribution, and recoil corrections. The nonrelativistic limit of the CI results is in excellent agreement with variational calculations. The theoretical values obtained for the hyperfine splitting are complete to the relative order of α^2 and improve upon results of previous studies.

physics.atom-ph↗

arXiv2007

QED calculation of the 2p3/2-2p1/2 transition energy in five-electron ion of argon

We perform ab initio QED calculation of the (1s)^2(2s)^22p_{3/2} - (1s)^2(2s)^22p_{1/2} transition energy in the five-electron ion of argon. The calculation is carried out by perturbation theory starting with an effective screening potential approximation. Four different types of the screening potentials are considered. The rigorous QED calculations of the two lowest-order QED and electron-correlation effects are combined with approximate evaluations of the third- and higher-order electron-correlation contributions. The theoretical value for the wavelength obtained amounts to 441.261(70) (nm, air) and perfectly agrees with the experimental one, 441.2559(1) (nm, air).

physics.atom-ph↗

arXiv2007

QED treatment of electron correlation in Li-like ions

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.

physics.atom-ph↗

arXiv2006

Non-perturbative 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.

physics.atom-ph↗

arXiv2006

Two-loop QED corrections in few-electron ions

Results of a calculation valid to all orders in the nuclear-strength parameter Zαare presented for the two-loop Lamb shift, notably for the two-loop self-energy correction, for the ground and first excited states of ions with the nuclear charge numbers Z=60-100. A detailed comparison of the all-order calculation with earlier investigations based on an expansion in the parameter Zαis given. The calculation removes the largest theoretical uncertainty for the 2p_j-2s transition energies in heavy Li-like ions and is important for interpretation of experimental data.

physics.atom-ph↗

arXiv2006

Quantum electrodynamics of heavy ions and atoms

The present status of quantum electrodynamics (QED) theory of heavy few-electron ions is reviewed. The theoretical results are compared with available experimental data. A special attention is focused on tests of QED at strong fields and on determination of the fundamental constants. A recent progress on calculations of the QED corrections to the parity nonconserving 6s-7s transition amplitude in neutral Cs is also discussed.

physics.atom-ph↗

arXiv2006

Mass Measurements and the Bound--Electron g Factor

The accurate determination of atomic masses and the high-precision measurement of the bound-electron g factor are prerequisites for the determination of the electron mass, which is one of the fundamental constants of nature. In the 2002 CODATA adjustment [P. J. Mohr and B. N. Taylor, Rev. Mod. Phys. 77, 1 (2005)], the values of the electron mass and the electron-proton mass ratio are mainly based on g factor measurements in combination with atomic mass measurements. In this paper, we briefly discuss the prospects for obtaining other fundamental information from bound-electron g factor measurements, we present some details of a recent investigation of two-loop binding corrections to the g factor, and we also investigate the radiative corrections in the limit of highly excited Rydberg S states with a long lifetime, where the g factor might be explored using a double resonance experiment.

physics.atom-ph↗

arXiv2005

QED Effects in Heavy Few-Electron Ions

Accurate calculations of the binding energies, the hyperfine splitting, the bound-electron g-factor, and the parity nonconservation effects in heavy few-electron ions are considered. The calculations include the relativistic, quantum electrodynamic (QED), electron-correlation, and nuclear effects. The theoretical results are compared with available experimental data. A special attention is focused on tests of QED in a strong Coulomb field.

physics.atom-ph↗

arXiv2005

Radiative and correlation effects on the parity-nonconserving transition amplitude in heavy alkaline atoms

The complete gauge-invariant set of the one-loop QED corrections to the parity-nonconserving (PNC) amplitude in cesium and francium is evaluated to all orders in $αZ$ using a local form of the Dirac-Fock potential. The calculations are performed in both length and velocity gauges for the absorbed photon and the total binding QED correction is found to be $-$0.27(3)% for Cs and $-$0.28(5)% for Fr. Moreover, a high-precision calculation of the electron-correlation and Breit-interaction effects on the 7$s-8s$ PNC amplitude in francium using a large-scale configuration-interaction Dirac-Fock method is performed. The obtained results are employed to improve the theoretical predictions for the PNC transition amplitude in Cs and Fr. Using an average value from two most accurate measurements of the vector transition polarizability, the weak charge of $^{133}$Cs is derived to amount to $ Q_W=-72.65(29)_{\rm exp}(36)_{\rm theor}$. This value deviates by $1.1σ$ from the prediction of the standard model. The values of the $7s$-$8s$ PNC amplitude in $^{223}$Fr and $^{210}$Fr are obtained to be $-$15.49(15) and $-$14.16(14), respectively, in units of i$\times 10^{-11}(-Q_W)/N$ a.u.

physics.atom-ph↗

arXiv2005

Improved all-order results for the one-loop QED correction to the hyperfine structure in light H-like atoms

A calculation of the one-loop self-energy and vacuum-polarization corrections to the hyperfine splitting of the 1s and 2s states in light H-like ions is carried out to all orders in the parameter Z α. Using the known values for the Z α-expansion coefficients, the numerical data obtained are extrapolated from Z=5 and higher to Z=0, 1, and 2, with the resulting accuracy being significantly better than in previous evaluations. Our calculation shifts the theoretical value of the normalized difference of the 1s and 2s hyperfine-structure intervals in ^3He^+ by 0.056 kHz and improves its accuracy.

physics.atom-ph↗

arXiv2005

QED corrections to the parity-nonconserving 6s-7s amplitude in $^{133}$Cs

The complete gauge-invariant set of the one-loop QED corrections to the parity-nonconserving 6s-7s amplitude in $^{133}$Cs is evaluated to all orders in $αZ$ using a local version of the Dirac-Hartree-Fock potential. The calculations are peformed in both length and velocity gauges for the absorbed photon. The total binding QED correction is found to be -0.27(3)%, which differs from previous evaluations of this effect. The weak charge of $^{133}$Cs, derived using two most accurate values of the vector transition polarizability $β$, is $Q_W=-72.57(46)$ for $β= 26.957(51) a_{\rm B}^3$ and $Q_W=-73.09(54)$ for $β= 27.15(11)a_{\rm B}^3 $. The first value deviates by $1.1σ$ from the prediction of the Standard Model, while the second one is in perfect agreement with it.

physics.atom-ph↗

arXiv2005

QED calculation of the n=1 and n=2 energy levels in He-like ions

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 $\aZ$. Uncalculated contributions to energy levels come through orders $α^3 (\aZ)^2$, $α^2 (\aZ)^7$, and higher. The calculation presented is the first treatment for excited states of He-like ions complete through order $α^2 (\aZ)^4$. A significant improvement in accuracy of theoretical predictions is achieved, especially in the high-$Z$ region.

physics.atom-ph↗

arXiv2004

Screened self-energy correction to the 2p3/2-2s transition energy in Li-like ions

We present an ab initio calculation of the screened self-energy correction for (1s)^2 2p3/2 and (1s)^2 2s states of Li-like ions with nuclear charge numbers in the range Z = 12-100. The evaluation is carried out to all orders in the nuclear-strength parameter Z α. This investigation concludes our calculations of all two-electron QED corrections for the 2p3/2-2s transition energy in Li-like ions and thus considerably improves theoretical predictions for this transition for high-Z ions.

physics.atom-ph↗

arXiv2004

Two-loop self-energy contribution to the Lamb shift in H-like ions

The two-loop self-energy correction is evaluated to all orders in Zαfor the ground-state Lamb shift of H-like ions with Z >= 10, where Z is the nuclear charge number and αis the fine structure constant. The results obtained are compared with the analytical values for the Zα-expansion coefficients. An extrapolation of the all-order numerical results to Z=1 is presented and implications of our calculation for the hydrogen Lamb shift are discussed.

hep-ph↗