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I. I. Tupitsyn

Publications and source records attributed to I. I. Tupitsyn.

At least 55 records · Page 3Linked to original sources
arXiv2019

QED calculation of electron-electron correlation effects in heliumlike ions

Fully relativistic approach to evaluate the correlation effects in highly charged ions is presented. The interelectronic-interaction contributions of first and second orders in $1/Z$ are treated rigorously within the framework of bound-state quantum electrodynamics, whereas the calculations of the third- and higher-order contributions are based on the Dirac-Coulomb-Breit Hamiltonian. The developed approach allows one to deal with single as well as degenerate or quasi-degenerate states. We apply this approach to the calculations of the correlation contributions to the $n=1$ and $n=2$ energy levels in heliumlike ions. The obtained contributions are combined with the one-electron and screened QED corrections, nuclear recoil and nuclear polarization corrections to get the total theoretical predictions for the ionization and transition energies in high-$Z$ heliumlike ions.

physics.atom-ph↗
arXiv2019

Relativistic calculations of the ground and inner-L-shell excited energy levels of berylliumlike ions

Large-scale relativistic configuration-interaction method combined with many-body perturbation theory is consistently applied to calculations of the energy levels of the ground and inner-L-shell excited states of berylliumlike ions in the range $10 \leq Z \leq 92$. The quantum electrodynamics, nuclear recoil, and frequency-dependent Breit corrections are taken into account. The obtained results are supplemented with the systematical estimation of the uncertainties.

physics.atom-ph↗
arXiv2019

Isotope shifts of the $1s^22s2p(J)$ -$1s^22s^2$ transition energies in Be-like thorium and uranium

Precise calculations of the isotope shifts in berylliumlike thorium and uranium ions are presented. The main contributions to the field and mass shifts are calculated within the framework of the Dirac-Coulomb-Breit Hamiltonian employing the configuration-interaction Dirac-Fock-Sturm method. These calculations include the relativistic, electron-electron correlation, and Breit-interaction effects. The QED, nuclear deformation, and nuclear polarization corrections are also evaluated.

physics.atom-ph↗
arXiv2018

QED calculations of the $n=2$ to $n=1$ x-ray transition energies in middle-$Z$ heliumlike ions

Ab initio QED calculations of the four x-ray transitions from the $L$ to $K$ shell in heliumlike argon, titanium, iron, copper, and krypton are performed. The binding energies for all the $n=1$ and $n=2$ states are evaluated as well. The calculation approach combines the rigorous QED treatment in the first two orders of the perturbation theory constructed within the extended Furry picture with the third- and higher-order correlation effects evaluated in the Breit approximation. The obtained results are compared with the previous evaluations and available experimental data.

physics.atom-ph↗
arXiv2018

Stringent tests of QED using highly charged ions

The present status of tests of QED with highly charged ions is reviewed. The theoretical predictions for the Lamb shift and the transition energies are compared with available experimental data. Recent achievements in studies of the hyperfine splitting and the $g$-factor isotope shift with highly charged ions are reported. Special attention is paid to tests of QED within and beyond the Furry picture at strong-coupling regime. Prospects for tests of QED at supercritical fields that can be created in low-energy heavy-ion collisions are discussed as well.

physics.atom-ph↗
arXiv2018

Relativistic nuclear recoil effect on the $g$ factor of highly charged boronlike ions

The nuclear recoil effect on the $g$ factor of the ground state of highly charged B-like ions is studied to first order in the electron-to-nucleus mass ratio $m/M$. The leading one-electron and two-electron recoil contributions are calculated nonperturbatively in the parameter $αZ$ within the rigorous QED formalism. The interelectronic-interaction correction to the nuclear recoil effect is evaluated in the Breit approximation by means of perturbation theory to the first order in $1/Z$. The higher-order interelectronic-interaction corrections are taken into account partially by performing the calculations with the effective screening potential. The results obtained represent the most accurate up-to-date treatment of the nuclear recoil effect on the $g$ factor of highly charged B-like ions in the range $Z = 20$--$92$.

physics.atom-ph↗
arXiv2018

Nuclear recoil effect on the g factor of highly charged Li-like ions

The nuclear recoil effect on the g factor of highly charged Li-like ions is evaluated in the range Z=10-92. The calculations are performed using the 1/Z perturbation theory. The one-electron recoil contribution is evaluated within the fully relativistic approach with the wave functions which account for the screening effects approximately. The two-electron recoil contributions of the first and higher orders in 1/Z are calculated within the Breit approximation using a four-component approach.

physics.atom-ph↗
arXiv2018

Relativistic calculations of X-Ray transition energies and isotope shifts in heavy atoms

X-Ray transition energies and isotope shifts in heavy atoms are evaluated. The energy levels with vacancies in the inner shells are calculated within the approximation of the average of nonrelativistic configuration employing the Dirac-Fock-Sturm method. The obtained results are compared with other configuration-interaction theoretical calculations and with experimental data.

physics.atom-ph↗
arXiv2018

One-center calculations of the electron-positron pair creation in low-energy collisions of heavy bare nuclei

The probabilities of bound-free electron-positron pair creation are calculated for head-on collisions of bare uranium nuclei beyond the monopole approximation. The calculations are based on the numerical solving of the time-dependent Dirac equation in the target reference frame with multipole expansion of the projectile potential. In addition, the energy dependence of the pair-creation cross section is studied in the monopole approximation.

physics.atom-ph↗
arXiv2018

Binding energies of the $1s^2\,2s\,2p\, ^3P_{0,2}$ states of berylliumlike xenon

Binding energies of the $^3P_0$ and $^3P_2$ levels of the $1s^2\,2s\,2p$ electron configuration in berylliumlike xenon are rigorously evaluated using ab initio QED approach. All relevant one- and many-electron QED contributions are accounted for up to the second order of the perturbation theory. The interelectronic-interaction effects of the third and higher orders are considered within the Breit approximation. Nuclear recoil effect is taken into account as well. In addition, we study all possible levels of the configuration $1s^2\,2s\,2p$, namely $^1P_1$ and $^3P_{0,1,2}$, by means of the configuration-interaction Dirac-Fock-Sturm method in berylliumlike neon, iron, and xenon. In this case the QED effects are treated approximately within the model QED approach. The obtained theoretical predictions are compared with the results of previous relativistic calculations and high-precision measurements.

physics.atom-ph↗
arXiv2017

Recoil effect on the g factor of Li-like ions

The nuclear recoil effect on the $g$ factor of Li-like ions is evaluated. The one-electron recoil contribution is treated within the framework of the rigorous QED approach to first order in the electron-to-nucleus mass ratio $m/M$ and to all orders in the parameter $αZ$. These calculations are performed in a range $Z=3-92$. The two-electron recoil term is calculated for low- and middle-$Z$ ions within the Breit approximation using a four-component approach. The results for the two-electron recoil part obtained in the paper strongly disagree with the previous calculations performed using an effective two-component Hamiltonian. The obtained value for the recoil effect is used to calculate the isotope shift of the $g$ factor of Li-like $^{A}$Ca$^{17+}$ with $A=40$ and $A=48$ which was recently measured. It is found that the new theoretical value for the isotope shift is closer to the experimental one than the previously obtained value.

physics.atom-ph↗
arXiv2017

Nuclear recoil effect on $g$ factor of heavy ions: prospects for tests of quantum electrodynamics in a new region

The nuclear recoil effect on the $g$ factor of H- and Li-like heavy ions is evaluated to all orders in $αZ$. The calculations include an approximate treatment of the nuclear size and the electron-electron interaction corrections to the recoil effect. As the result, the second largest contribution to the theoretical uncertainty of the $g$-factor values of $^{208}$Pb$^{79+}$ and $^{238}$U$^{89+}$ is strongly reduced. Special attention is paid to tests of the QED recoil effect on the $g$ factor in experiments with heavy ions. It is found that, while the QED recoil effect on the $g$-factor value is masked by the uncertainties of the nuclear size and nuclear polarization contributions, it can be probed on a few-percent level in the specific difference of the $g$ factors of H- and Li-like heavy ions. This provides a unique opportunity to test QED in a new region --- strong-coupling regime beyond the Furry picture.

physics.atom-ph↗
arXiv2017

Nuclear recoil effect on the g factor of middle-Z boronlike ions

The nuclear recoil correction to the g factor of boronlike ions is evaluated within the lowest-order relativistic (Breit) approximation. The interelectronic-interaction effects are taken into account to the first order of the perturbation theory in 1/Z. Higher orders in 1/Z are partly accounted for by means of the effective screening potential. The most accurate up-to-date values of this contribution are presented for the ions in the range Z=10-20.

physics.atom-ph↗
arXiv2017

Ground-state ionization energies of boronlike ions

High-precision QED calculations of the ground-state ionization energies are performed for all boronlike ions with the nuclear charge numbers in the range $16 \leqslant Z\leqslant 96$. The rigorous QED calculations are performed within the extended Furry picture and include all many-electron QED effects up to the second order of the perturbation theory. The contributions of the third- and higher-order electron-correlation effects are accounted for within the Breit approximation. The nuclear recoil and nuclear polarization effects are taken into account as well. In comparison with the previous evaluations of the ground-state ionization energies of boronlike ions the accuracy of the theoretical predictions has been improved significantly.

physics.atom-ph↗
arXiv2017

Relativistic calculations of differential ionization cross sections: Application to antiproton-hydrogen collisions

A new relativistic method based on the Dirac equation for calculating fully differential cross sections for ionization in ion-atom collisions is developed. The method is applied to ionization of the atomic hydrogen by antiproton impact, as a non-relativistic benchmark. The fully differential, as well as various doubly and singly differential cross sections for ionization are presented. The role of the interaction between the projectile and the target nucleus is discussed. Several discrepancies in available theoretical predictions are resolved. The relativistic effects are studied for ionization of hydrogenlike xenon ion under the impact of carbon nuclei.

physics.atom-ph↗
arXiv2016

Effective three particle forces in polyvalent atoms

We study effective three-particle interactions between valence electrons, which are induced by the core polarization. Such interactions are enhanced when valence orbitals have strong overlap with the outermost core shell, in particular for the systems with partially filled f-shell. We find that in certain cases the three-particle contributions are large, affecting the order of energy levels, and need to be included in high-precision calculations.

physics.atom-ph↗
arXiv2016

QED shifts in multivalent heavy ions

The quantum electrodynamics (QED) corrections are directly incorporated into the most accurate treatment of the correlation corrections for ions with complex electronic structure of interest to metrology and tests of fundamental physics. We compared the performance of four different QED potentials for various systems to access the accuracy of QED calculations and to make prediction of highly charged ion properties urgently needed for planning future experiments. We find that all four potentials give consistent and reliable results for ions of interest. For the strongly bound electrons the nonlocal potentials are more accurate than the local potential.

physics.atom-ph↗