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V. A. Dzuba

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

At least 181 records · Page 10Linked to original sources
arXiv2006

Calculation of energy levels and transition amplitudes for barium and radium

The radium atom is a promising system for studying parity and time invariance violating weak interactions. However, available experimental spectroscopic data for radium is insufficient for designing an optimal experimental setup. We calculate the energy levels and transition amplitudes for radium states of significant interest. Forty states corresponding to all possible configurations consisting of the $7s$, $7p$ and $6d$ single-electron states as well as the states of the $7s8s$, $7s8p$ and $7s7d$ configurations have been calculated. The energies of ten of these states corresponding to the $6d^2$, $7s8s$, $7p^2$, and $6d7p$ configurations are not known from experiment. Calculations for barium are used to control the accuracy.

physics.atom-ph↗
arXiv2006

Frequency shift of hyperfine transitions due to blackbody radiation

We have performed calculations of the size of the frequency shift induced by a static electric field on the clock transition frequencies of the hyperfine splitting in Yb+, Rb, Cs, Ba+, and Hg+. The calculations are used to find the frequency shifts due to blackbody radiation which are needed for accurate frequency measurements and improvements of the limits on variation of the fine structure constant, alpha. Our result for Cs (delta nu E^2=-2.26 times 10^{-10}Hz/(V/m)^2) is in good agreement with early measurements and ab initio calculations. We present arguments against recent claims that the actual value might be smaller. The difference (approx 10%) is due to the contribution of the continuum spectrum in the sum over intermediate states.

physics.atom-ph↗
arXiv2006

Frequency shift of cesium clock transition due to blackbody radiation

We have performed ab initio calculations of the frequency shift induced by a static electric field on the cesium clock hyperfine transition. The calculations are used to find the frequency shifts due to blackbody radiation. Our result ($δν/E^2=-2.26(2)\times 10^{-10}$Hz/(V/m)$^2$) is in good agreement with early measurements and ab initio calculations performed in other groups. We present arguments against recent claims that the actual value of the effect might be smaller. The difference ($\sim$ 10%) between ab initio and semiempirical calculations is due to the contribution of the continuum spectrum to the sum over intermediate states.

physics.atom-ph↗
arXiv2006

Laboratory spectroscopy and the search for space-time variation of the fine structure constant using QSO spectra

Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental ``constants'' in the Universe. A change in the fine structure constant, alpha, could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Previous studies of three independent samples of data, containing 143 absorption systems spread from 2 to 10 billion years after big bang, hint that alpha was smaller 7 - 11 billion years ago. To continue this study we urgently need accurate laboratory measurements of atomic transition frequencies. In this paper, we present a current list of transitions of importance to the search for alpha variation. They are E1 transitions to the ground state in several different atoms and ions, with wavelengths ranging from around 900 - 6000 Angstroms, and require an accuracy of better than 10^(-4) Angstroms. We also discuss isotope shift measurements that are needed in order to resolve systematic effects in the study. Researchers who are interested in performing these measurements should contact the authors directly.

physics.atom-ph↗
arXiv2005

Breit Interaction and Parity Non-conservation in Many-Electron Atoms

We present accurate {\em ab initio} non-perturbative calculations of the Breit correction to the parity non-conserving (PNC) amplitudes of the $6s-7s$ and $6s-5d_{3/2}$ transitions in Cs, $7s-8s$ and $7s-6d_{3/2}$ transitions in Fr, $6s-5d_{3/2}$ transition in Ba$^+$, $7s-6d_{3/2}$ transition in Ra$^+$, and $6p_{1/2} - 6p_{3/2}$ transition in Tl. The results for the $6s-7s$ transition in Cs and $7s-8s$ transition in Fr are in good agreement with other calculations while calculations for other atoms/transitions are presented for the first time. We demonstrate that higher-orders many-body corrections to the Breit interaction are especially important for the $s-d$ PNC amplitudes. We confirm good agreement of the PNC measurements for cesium and thallium with the standard model .

physics.atom-ph↗
arXiv2005

Calculations of energy levels and lifetimes of low-lying states of barium and radium

We use the configuration interaction method and many-body perturbation theory to perform accurate calculations of energy levels, transition amplitudes, and lifetimes of low-lying states of barium and radium. Calculations for radium are needed for the planning of measurements of parity and time invariance violating effects which are strongly enhanced in this atom. Calculations for barium are used to control the accuracy of the calculations.

physics.atom-ph↗
arXiv2005

A New Option for a Search for Alpha Variation: Narrow Transitions with Enhanced Sensitivity

We consider several transitions between narrow lines that have an enhanced sensitivity to a possible variation of the fine structure constant, alpha. This enhancement may allow a search to be performed with an effective suppression of the systematic sources of uncertainty that are unavoidable in conventional high-resolution spectroscopic measurements. In the future this may provide the strongest laboratory constraints on alpha variation.

physics.atom-ph↗
arXiv2005

Fine Structure Anomalies and Search for Variation of the Fine Structure Constant in Laboratory Experiments

Configuration interaction in many-electron atoms may cause anomalies in the fine structure which make the intervals small and very sensitive to variation of the fine structure constant. Repeated precision measurements of these intervals over long period of time can put strong constrain on possible time variation of the fine structure constant. We consider the $5p^4 \ ^3$P$_{2,1,0}$ fine structure multiplet in the ground state of neutral tellurium as an example. Here the effect of change of the fine structure constant is enhanced about one hundred times in the relative change of the small energy interval between the $^3$P$_1$ and $^3$P$_0$ states.

physics.atom-ph↗
arXiv2005

Calculation of isotope shifts for cesium and francium

We perform ab initio calculations of isotope shifts for isotopes of cesium (from A=123 to A=137) and francium (from A=207 to A=228). These calculations start from the relativistic Hartree-Fock method and make use of several techniques to include correlations. The field (volume) isotope shift is calculated by means of an all-order correlation potential method and within the singles-doubles partial triples linearized coupled-cluster approach. Many-body perturbation theory in two different formulations is used to calculate the specific mass shift. We discuss the strong points and shortcomings of the different approaches and implications for parity nonconservation in atoms. Changes in nuclear charge radii are found by comparing the present calculations with experiment.

physics.atom-ph↗
arXiv2005

Calculation of the energy levels of Ge, Sn, Pb and their ions in the $V^{N-4}$ approximation

Energy levels of germanium, tin and lead together with their single, double and triple ionized positive ions have been calculated using the $V^{N-M}$ approximation suggested in the previous work (Dzuba, physics/0501032) (M=4 - number of valence electrons). Initial Hartree-Fock calculations are done for the quadruply ionized ions with all valence electrons removed. The core-valence correlations are included beyond the second-order of the many-body perturbation theory. Interaction between valence electrons is treated by means of the configuration interaction technique. It is demonstrated that accurate treatment of the core-valence correlations lead to systematic improvement of the accuracy of calculations for all ions and neutral atoms.

physics.atom-ph↗
arXiv2005

Relativistic energy shifts in Ge II, Sn II and Pb II and search for cosmological variation of the fine structure constant

Sensitivity of atomic transition frequencies to variation of the fine structure constant $α=e^2/\hbar c$ increases proportional to $Z^2$ where $Z$ is the nuclear charge. Recently several lines of heavy ions Ge II, Sn II and Pb II have been detected in quasar absorption spectra. We have performed accurate many-body calculations of $α^2$-dependence of transition frequencies ($q$-coefficients) for these atoms and found an order of magnitude increase in sensitivity in comparison with atomic transitions which were previously used to search for temporal and spatial variation of $α$ in quasar absorption systems. An interesting feature in Pb II is highly non-linear dependence on $α^2$ due to the level pseudo-crossings.

astro-ph↗
arXiv2005

On the use of the $V^{N-M}$ approximation in atomic calculations

We demonstrate that $V^{N-M}$ approximation is a good starting point for the configuration interaction calculations for many-electron atoms and ions. $N$ is the total number of electrons in the neutral atom, $M$ is the number of valence electrons. $V^{N-M}$ is the self-consistent Hartree Fock potential for a closed-shell ion with all valence electrons removed. Using of the $V^{N-M}$ approximation considerably simplifies the many-body perturbation theory for the core-valence correlations. It makes it easier to include higher-order correlations which often significantly improves the accuracy of the calculations. Calculations for krypton and barium and their positive ions are presented for illustration.

physics.atom-ph↗
arXiv2004

Atomic Clocks and the Search for Variation of the Fine Structure Constant

Evidence that the fine structure constant, alpha, was different in an early epoch has recently been found in quasar (QSO) absorption spectra. An accurate laboratory measurement of alpha variation could help to distinguish between space and time variation of alpha and possibly confirm the QSO results. We have performed calculations of the relativistic energy shifts that a variation of alpha would cause in a wide range of atomic spectra. A laboratory measurement of how these transition frequencies vary over time is vital in determining whether alpha is varying today.

physics.atom-ph↗
arXiv2004

Space-time variation of the fine structure constant and evolution of isotope abundances

At present several groups are analyzing astrophysical data in a search for time-variation of the fine structure constant $α$. Here we discuss how to exclude systematic effects caused by the changes in the isotope abundances during the evolution of the universe. We suggest using particular combinations of the transition frequencies of O II, Al II, Al III, Si II and Mn II as anchors, which are insensitive to $α$-variation and to changes in isotope abundances. These anchors can be used to determine the cosmological redshift. Then, one can use other combinations of frequencies as probes for the time-variation of $α$ and another set as probes for the isotopic abundances. In this way it is possible to eliminate one source of the systematic errors in the search for $α$-variation and get new information about evolution of the isotopes. On the level of accuracy that has already been reached in the search for $α$-variation it is possible to see ~10% changes in isotope abundances of Si and Ni.

astro-ph↗
arXiv2004

The alpha-dependence of transition frequencies for some ions of Ti, Mn, Na, C, and O, and the search for variation of the fine structure constant

We use the relativistic Hartree-Fock method, many-body perturbation theory and configuration-interaction method to calculate the dependence of atomic transition frequencies on the fine structure constant, alpha. The results of these calculations will be used in the search for variation of the fine structure constant in quasar absorption spectra.

physics.atom-ph↗
arXiv2004

Relativistic effects in two valence electron atoms and ions and the search for variation of the fine structure constant

We perform accurate calculations of the dependence of transition frequencies in two valence electron atoms and ions on a variation of the fine structure constant, alpha. The relativistic Hartree-Fock method is used with many-body perturbation theory and configuration interaction methods to calculate transition frequencies. The results are to be used in atomic-clock-type laboratory experiments designed to test whether alpha varies in time.

physics.atom-ph↗
arXiv2003

Configuration interaction calculation for the isotope shift in Mg I

We present an ab initio method of calculation of isotope shift in atoms with a few valence electrons, based on the configuration-interaction calculation of energy. The main motivation for developing the method comes from the need to analyze whether differences in isotope abundance in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine structure constant, alpha, was smaller at early epoch. We show that we can calculate the isotope shift in magnesium with good accuracy.

physics.atom-ph↗