arXiv subjects

V. A. Dzuba

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

At least 163 records · Page 9Linked to original sources

arXiv2009

Calculation of Stark-induced absorption on the 6s6p ^3P_1 - 6s^2 ^1S_0 transition in Hg

We carry out relativistic many-body calculations of the Stark-induced absorption coefficient on the 254-nm $6s6p ^3P_1 (F=1/2) - 6s^2 ^1S_0$ line of $^{199}$Hg atom, the effect considered before by Lamoreaux and Fortson using a simple central field estimate [Phys. Rev. A {\bf 46}, 7053 (1992)]. The Stark-induced admixing of states of opposite parity opens additional M1 and E2 transition channels. We find that the resulting M1-E1 absorption dominates over E2-E1 absorption. The value of the E2-E1 absorption coefficient depends strongly on the details of treatment of the correlation problem. As a result, our numerical values differ substantially from those of the earlier central field calculation. Reliable calculation of this effect can enable a useful experimental check on the optical technique being used to search for a permanent electric dipole moment of the $^{199}$Hg atom.

physics.atom-ph↗

arXiv2009

An universal algorithm of calculating terms of atomic many-body perturbation theory

An algorithm, based on numerical description of the terms of many-body perturbation theory (Goldstone diagrams), is presented. The algorithm allows the use of the same piece of computer code to evaluate any particular diagram in any specific order of the perturbation theory or to calculate similar terms in other areas of the many-body theory, like e.g. terms in the coupled-cluster equations. The use of the algorithm is illustrated by calculating the second and third order correlation corrections to the removal energies of electrons from the ground state of sodium, copper and gallium and by calculating the hyperfine structure constants of sodium in the linearized single-double coupled cluster approximation.

physics.atom-ph↗

arXiv2008

AC Stark shift of the Cs microwave atomic clock transitions

We analyze the AC Stark shift of the Cs microwave atomic clock transition theoretically and experimentally. Theoretical and experimental data are in a good agreement with each other. Results indicate the absence of a magic wavelength at which there would be no differential shift of the clock states having zero projections of the total angular momentum.

physics.atom-ph↗

arXiv2008

Magic frequencies for cesium primary frequency standard

We consider microwave hyperfine transitions in the ground state of cesium and rubidium atoms which are presently used as the primary and the secondary frequency standards. The atoms are confined in an optical lattice generated by a circularly polarized laser field. We demonstrate that applying an external magnetic field with appropriately chosen direction may cancel dynamic Stark frequency shift making the frequency of the clock transition insensitive to the strengths of both the laser and the magnetic fields. This can be attained for practically any laser frequency which is sufficiently distant from a resonance.

physics.atom-ph↗

arXiv2008

Calculation of the spectrum of the superheavy element Z=120

High-precision calculations of the energy levels of the superheavy element Z=120 are presented. The relativistic Hartree-Fock and configuration interaction techniques are employed. The correlations between core and valence electrons are treated by means of the correlation potential method and many-body perturbation theory. Similar calculations for barium and radium are used to gauge the accuracy of the calculations and to improve the ab initio results.

physics.atom-ph↗

arXiv2008

Micromagic clock: microwave clock based on atoms in an engineered optical lattice

We propose a new class of atomic microwave clocks based on the hyperfine transitions in the ground state of aluminum or gallium atoms trapped in optical lattices. For these elements magic wavelengths exist at which both levels of the hyperfine doublet are shifted at the same rate by the lattice laser field, cancelling its effect on the clock transition. Our analysis of various systematic effects shows that, while offering an improved control over systematic errors, the accuracy of the proposed microwave clock is competitive to that of the state-of-the-art primary frequency standard.

physics.atom-ph↗

arXiv2008

Correlation potential and ladder diagrams

The all-order correlation potential method of accurate atomic structure calculations for atoms with one external electron is extended to include one more class of correlation diagrams to all orders. These are the so-called ladder diagrams which describe residual Coulomb interaction between an external electron and atomic core. This is in addition to the screening of Coulomb interaction by core electrons and the hole-particle interaction in the core polarization operator which are also included in all orders. Calculations of the energies of the lowest $s$, $p$ and $d$ states of cesium and thallium show that inclusion of the ladder diagrams leads to significant improvement of the accuracy of the calculations. The discrepancy between theoretical and experimental energies is reduced to a small fraction of a per cent in all cases. This widens the range of atoms and atomic states for which the correlation potential method can produce very accurate results.

physics.atom-ph↗

arXiv2008

The effect of atomic electrons on nuclear fission

We calculate correction to the nuclear fission barrier produced by the atomic electrons. The result presented in analytical form is convenient to use in future nuclear calculations. The atomic electrons have a small stabilizing effect on nuclei, increasing lifetime in nuclear fission channel. This effect gives a new instrument to study the fission process.

physics.atom-ph↗

arXiv2008

Calculations of the spectra of superheavy elements E119 and E120+

High-precision calculations of the energy levels of the superheavy elements E119 and E120+ are presented. Dominating correlation corrections beyond relativistic Hartree-Fock are included to all orders in the Coulomb interaction using the Feynman diagram technique and the correlation potential method. The Breit interaction and quantum electrodynamics radiative corrections are considered. Also, the volume isotope shift is determined. A similar treatment for Cs, Fr, Ba+ and Ra+ is used to gauge the accuracy of the calculations and to refine the ab initio results.

physics.atom-ph↗

arXiv2008

Search for variation of the fundamental constants in atomic, molecular and nuclear spectra

The search for variation of the fundamental constants such as the fine structure constant $α$ ($α=e^2/\hbar c$) and the ratios of fundamental masses (e.g., electron to proton mass ratio $μ=m_e/m_p$) is reviewed. Strong emphasis is given to establishing the relationships between the change in the measured frequencies of atomic, molecular or nuclear transitions and the corresponding change of the fundamental constants. Transitions in which the sensitivity of the frequency change to the variation of the fine structure constant is strongly enhanced are discussed and most recent experimental results are presented. Most attention is given to the use of atomic, molecular and nuclear transitions in the study of quasar absorption spectra and in atomic clock experiments.

physics.atom-ph↗

arXiv2008

Atomic calculations and search for variation of the fine structure constant in quasar absorption spectra

A brief review of the search for variation of the fine structure constant in quasar absorption spectra is presented. Special consideration is given to the role of atomic calculations in the analysis of the observed data. A range of methods which allow to perform calculations for atoms or ions with different electron structure and which cover practically all periodic table of elements is discussed. Critical compilation of the results of the calculations as well as a review of the most recent results of the analysis are presented.

physics.atom-ph↗

arXiv2008

Nuclear magnetic octupole moment and the hyperfine structure of the $5D_{3/2,5/2}$ states of the Ba$^+$ ion

The hyperfine structure of the long-lived $5D_{3/2}$ and $5D_{5/2}$ levels of Ba$^+$ ion is analyzed. A procedure for extracting relatively unexplored nuclear magnetic moments $Ω$ is presented. The relevant electronic matrix elements are computed in the framework of the ab initio relativistic many-body perturbation theory. Both the first- and the second-order (in the hyperfine interaction) corrections to the energy levels are analyzed. It is shown that a simultaneous measurement of the hyperfine structure of the entire $5D_J$ fine-structure manifold allows one to extract $Ω$ without contamination from the second-order corrections. Measurements to the required accuracy should be possible with a single trapped barium ion using sensitive techniques already demonstrated in Ba$^+$ experiments.

physics.atom-ph↗

arXiv2007

Relativistic corrections to transition frequencies of Ag I, Dy I, Ho I, Yb II, Yb III, Au I and Hg II and search for variation of the fine structure constant

Dependence of transition frequencies on the fine structure constant $α=e^2/\hbar c$ is calculated for several many-electron systems which are used or planned to be used in the laboratory search for the time variation of the fine structure constant. In systems with a large number of electrons in open shells (from 11 to 15) the relative effects of the variation may be strongly enhanced. For the transitions which were considered before the results are in good agreement with previous calculations.

physics.atom-ph↗

arXiv2007

Relativistic corrections to transition frequencies of Fe I and search for variation of the fine structure constant

Relativistic energy shifts of the low energy levels of Fe have been calculated using the Dirac-Hartree-Fock and configuration interaction techniques. The results are to be used in the search for the space-time variation of the fine structure constant in quasar absorption spectra. The values of the shifts are the largest among those used in the analysis so far. This makes Fe a good candidate for the inclusion into the analysis.

physics.atom-ph↗

arXiv2007

Many-body calculations of relativistic energy shifts for single- and double-valence atoms

Relativistic Hartree-Fock method together with many-body perturbation theory and configuration interaction techniques are used to calculate relativistic energy shifts for frequencies of the strong electric dipole transitions of C III, C IV, Na I, Mg I, Mg II, Al II, Al III, Si IV, Ca II and Zn II. These transitions are used for search of the variation of the fine structure constant in quasar absorption spectra. The results are in good agreement with previous calculations. The analysis of Breit contributions is also presented.

physics.atom-ph↗

arXiv2007

Coupled-cluster single-double calculations of the relativistic energy shifts in C IV, Na I, Mg II, Al III, Si IV, Ca II and Zn II

The relativistic coupled-cluster single-double method is used to calculate the dependence of frequencies of strong $E1$-transitions in many monovalent atoms and ions on the fine-structure constant $α$. These transitions are used in the search for manifestations of the variation of the fine-structure constant in quasar absorption spectra. Results of the present calculations are in good agreement with previous calculations but are more accurate.

physics.atom-ph↗

arXiv2007

Atomic electric dipole moments of He and Yb induced by nuclear Schiff moments

We have calculated the atomic electric dipole moments (EDMs) d of ^3He and ^{171}Yb induced by their respective nuclear Schiff moments S. Our results are d(He)= 8.3x10^{-5} and d(Yb)= -1.9 in units 10^{-17}S/(e{fm}^3)e cm. By considering the nuclear Schiff moments induced by the parity and time-reversal violating nucleon-nucleon interaction we find d(^{171}Yb)~0.6d(^{199}Hg). For ^3He the nuclear EDM coupled with the hyperfine interaction gives a larger atomic EDM than the Schiff moment. The result for ^3He is required for a neutron EDM experiment that is under development, where ^3He is used as a comagnetometer. We find that the EDM for He is orders of magnitude smaller than the neutron EDM. The result for Yb is needed for the planning and interpretation of experiments that have been proposed to measure the EDM of this atom.

physics.atom-ph↗

arXiv2007

Core-valence correlations for atoms with open shells

We present an efficient method of inclusion of the core-valence correlations into the configuration interaction (CI) calculations. These correlations take place in the core area where the potential of external electrons is approximately constant. A constant potential does not change the core electron wave functions and Green's functions. Therefore, all operators describing interaction of $M$ valence electrons and $N-M$ core electrons (the core part of the Hartree-Fock Hamiltonian $V^{N-M}$, the correlation potential $\hatΣ_1({\bf r},{\bf r'},E)$ and the screening of interaction between valence electrons by the core electrons $\hatΣ_2$) may be calculated with all $M$ valence electrons removed. This allows one to avoid subtraction diagrams which make accurate inclusion of the core-valence correlations for $M>2$ prohibitively complicated. Then the CI Hamiltonian for $M$ valence electrons is calculated using orbitals in complete $V^{N}$ potential (the mean field produced by all electrons); $\hatΣ_1$ + $\hatΣ_2$ are added to the CI Hamiltonian to account for the core-valence correlations. We calculate $\hatΣ_1$ and $\hatΣ_2$ using many-body perturbation theory in which dominating classes of diagrams are included in all orders. We use neutral Xe I and all positive ions up to Xe VIII as a testing ground. We found that the core electron density for all these systems is practically the same. Therefore, we use the same $\hatΣ_1$ and $\hatΣ_2$ to build the CI Hamiltonian in all these systems ($M=1,2,3,4,5,6,7,8$). Good agreement with experiment for energy levels and Landé factors is demonstrated for all cases from Xe I to Xe VIII.

physics.atom-ph↗