arXiv subjects

V. A. Dzuba

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

At least 127 records · Page 7Linked to original sources

arXiv2012

Ion clock and search for the variation of the fine structure constant using optical transitions in Nd$^{13+}$ and Sm$^{15+}$

We study ultranarrow $5s_{1/2}$ - $4f_{5/2}$ transitions in Nd$^{13+}$ and Sm$^{15+}$ and demonstrate that they lie in the optical region. The transitions are insensitive to external perturbations. At the same time they are sensitive to the variation of the fine structure constant $α$. The fractional accuracy of the frequency of the transitions can be smaller than $10^{-19}$, which may provide a basis for atomic clocks of superb accuracy. Sensitivity to the variation of $α$ approaches $10^{-20}$ per year.

physics.atom-ph↗

arXiv2012

Highly-charged ions as a basis of optical atomic clockwork of exceptional accuracy

We propose a novel class of atomic clocks based on highly charged ions. We consider highly-forbidden laser-accessible transitions within the $4f^{12}$ ground-state configurations of highly charged ions. Our evaluation of systematic effects demonstrates that these transitions may be used for building exceptionally accurate atomic clocks which may compete in accuracy with recently proposed nuclear clock.

physics.atom-ph↗

arXiv2012

Revisiting parity non-conservation in cesium

We apply the sum-over-states approach to calculate partial contributions to the parity non-conservation (PNC) in cesium [Porsev {\em et al}, Phys. Rev. D {\bf 82}, 036008 (2010)]. We have found significant corrections to two non-dominating terms coming from the contribution of the core and highly excited states ($n>9$, the so called {\em tail}). When these differences are taken into account the result of Porsev {\em et al}, $E_{\rm PNC} = 0.8906\,(24) \times 10^{-11}i(-Q_W/N)$ changes to $0.8977\,(40)$, coming into good agreement with our previous calculations, $0.8980\,(45)$. The interpretation of the PNC measurements in cesium still indicates reasonable agreement with the standard model ($1.5\,σ$), however gives new constraints on physics beyond it.

hep-ph↗

arXiv2012

Highly charged ions with E1, M1, and E2 transitions within laser range

Level crossings in the ground state of ions occur when the nuclear charge Z and ion charge Z_ion are varied along an isoelectronic sequence until the two outermost shells are nearly degenerate. We examine all available level crossings in the periodic table for both near neutral ions and highly charged ions (HCIs). Normal E1 transitions in HCIs are in X-ray range, however level crossings allow for optical electromagnetic transitions that could form the reference transition for high accuracy atomic clocks. Optical E1 (due to configuration mixing), M1 and E2 transitions are available in HCIs near level crossings. We present scaling laws for energies and amplitudes that allow us to make simple estimates of systematic effects of relevance to atomic clocks. HCI clocks could have some advantages over existing optical clocks because certain systematic effects are reduced, for example they can have much smaller thermal shifts. Other effects such as fine-structure and hyperfine splitting are much larger in HCIs, which can allow for richer spectra. HCIs are excellent candidates for probing variations in the fine-structure constant, alpha, in atomic systems as there are transitions with the highest sensitivity to alpha-variation.

physics.atom-ph↗

arXiv2012

Relativistic coupled-cluster single-double calculations of positron-atom bound states

Relativistic coupled-cluster single-double approximation is used to calculate positron-atom bound states. The method is tested on closed-shell atoms such as Be, Mg, Ca, Zn, Cd, and Hg where a number of accurate calculations is available. It is then used to calculate positron binding energies for a range of open-shell transition metal atoms from Sc to Cu, from Y to Pd, and from Lu to Pt. These systems possess Feshbach resonances, which can be used to search for positron-atom binding experimentally through resonant annihilation or scattering.

physics.atom-ph↗

arXiv2012

Chaos-induced enhancement of resonant multielectron recombination in highly charged ions: Statistical theory

A statistical theory of resonant multielectron recombination based on properties of chaotic eigenstates is developed. The level density of many-body states increases exponentially with the number of excited electrons. When the residual electron-electron interaction exceeds the interval between these levels, the eigenstates (called compound states or compound resonances if these states are in the continuum) become "chaotic" superpositions of large numbers of Hartree-Fock configurational basis states. This situation takes place in some rare-earth atoms and many open-shell multiply charged ions excited in the process of electron recombination. Our theory describes resonant multielectron recombination via dielectronic doorway states leading to such compound resonances. The result is a radiative capture cross section averaged over a small energy interval containing several compound resonances. In many cases individual resonances are not resolved experimentally (since the interval between them is small, e.g., $\le 1$ meV, possibly even smaller than their radiative widths), therefore, our statistical theory should correctly describe the experimental data. We perform numerical calculations of the recombination cross sections for tungsten ions W$^{q+}$, $q=18$--25. The recombination rate for W$^{20+}$ measured recently [Phys. Rev. A {\bf 83}, 012711 (2011)] is $10^3$ greater than the direct radiative recombination rate at low energies, and our result for W$^{20+}$ agrees with the measurements.

physics.atom-ph↗

arXiv2012

Optical transitions in highly-charged californium ions with high sensitivity to variation of the fine-structure constant

We study electronic transitions in highly-charged Cf ions that are within the frequency range of optical lasers and have very high sensitivity to potential variations in the fine-structure constant, alpha. The transitions are in the optical despite the large ionisation energies because they lie on the level-crossing of the 5f and 6p valence orbitals in the thallium isoelectronic sequence. Cf16+ is a particularly rich ion, having several narrow lines with properties that minimize certain systematic effects. Cf16+ has very large nuclear charge and large ionisation energy, resulting in the largest alpha-sensitivity seen in atomic systems. The lines include positive and negative shifters.

physics.atom-ph↗

arXiv2012

Relativistic ab initio calculations of the P-odd interaction constant W_A in diatomic molecules

We present ab initio calculations of the $W_A$ parameter of the P-odd spin-rotational Hamiltonian for a variety of diatomic molecules, including the group--2 and --12 halides. The results were obtained by relativistic Dirac--Hartree--Fock and density functional theory approaches, and corrected for core polarization effects. Strong enhancement of $W_A$ is found for the group--12 diatomic halides, which should be helpful in future determination of the nuclear anapole moment.

physics.atom-ph↗

arXiv2012

Relations between matrix elements of different weak interactions and interpretation of the PNC and EDM measurements in atoms and molecules

The relations between matrix elements of different P- and T-odd weak interactions are derived. We demonstrate that similar relations hold for parity nonconserving (PNC) transition amplitudes and electron electric dipole moments (EDM) of atoms and molecules. This allows to express P- and T-odd effects in many-electron systems caused by different symmetry-breaking mechanisms via each other using simple analytical formulas. We use these relations for the interpretation of the anapole moment measurements in cesium and thallium and for the analysis of the relative contributions of the scalar-pseudoscalar CP-odd weak interaction and electron EDM to the EDM of Cs, Tl, Fr and other atoms and many polar molecules (YbF, PbO, ThO, etc.). Model-independent limits on electron EDM and the parameter of the scalar-pseudoscalar CP-odd interaction are found from the analysis of the EDM measurements for Tl and YbF.

physics.atom-ph↗

arXiv2011

Parity nonconservation in hyperfine transitions

We use relativistic Hartree-Fock and correlation potential methods to calculate nuclear spin-dependent parity non-conserving amplitudes (dominated by the nuclear anapole moment) between hyperfine structure components of the ground state of odd isotopes of K, Rb, Cs, Ba+, Yb+, Tl, Fr, and Ra+. The results are to be used for interpretation of current and future measurements.

physics.atom-ph↗

arXiv2011

A Single-Ion Nuclear Clock for Metrology at the 19th Decimal Place

The 7.6(5) eV nuclear magnetic-dipole transition in a single 229Th3+ ion may provide the foundation for an optical clock of superb accuracy. A virtual clock transition composed of stretched states within the 5F5/2 electronic ground level of both nuclear ground and isomeric manifolds is proposed. It is shown to offer unprecedented systematic shift suppression, allowing for clock performance with a total fractional inaccuracy approaching 1 x 10^-19.

physics.atom-ph↗

arXiv2011

Comment on "Reappraisal of the Electric Dipole Moment Enhancement Factor for Thallium"

Recent paper by Nataraj {\em et al} (Phys. Rev. Lett. {\bf 106}, 200403 (2011)) presents calculations of the EDM enhancement factor for Tl, which disagrees with previous most accurate calculations. The authors claim that their calculations of Tl EDM are the most accurate due to more complete treatment of higher-order correlations. In this note we argue that this claim is not supported by sufficient evidence. Nataraj {\em et al} also present misleading comments about our calculations. We explain our method and reply to the Nataraj {\em et al} comments.

physics.atom-ph↗

arXiv2011

Transitions in Zr, Hf, Ta, W, Re, Hg, Ac and U ions with high sensitivity to variation of the fine-structure constant

We study transitions between ground and low-energy excited states of heavy ions corresponding to s-d single-electron transitions or s^2-d^2 double-electron transitions. The large nuclear charge Z and significant change in angular momentum of electron orbitals make these transitions highly sensitive to a potential variation in the fine-structure constant, alpha. The transitions may be considered as candidates for laboratory searches for space-time variation of alpha.

physics.atom-ph↗

arXiv2011

Calculation of nuclear-spin-dependent parity nonconservation in s-d transitions of Ba$^+$, Yb$^+$ and Ra$^+$ ions

We use correlation potential and many-body perturbation theory techniques to calculate spin-independent and nuclear spin-dependent parts of the parity nonconserving amplitudes of the transitions between the $6s_{1/2}$ ground state and the $5d_{3/2}$ excited state of Ba$^+$ and Yb$^+$ and between the $7s_{1/2}$ ground state and the $6d_{3/2}$ excited state of Ra$^+$. The results are presented in a form convenient for extracting of the constants of nuclear-spin-dependent interaction (such as, e.g., anapole moment) from the measurements.

physics.atom-ph↗

arXiv2011

Hole transitions in multiply-charged ions for precision laser spectroscopy and searching for alpha-variation

We consider transitions of electron holes (vacancies in otherwise filled shells of atomic systems) in multiply-charged ions that, due to level-crossing of the holes, have frequencies within the range of optical atomic clocks. Strong E1 transitions provide new options for laser-cooling and trapping, while narrow transitions can be used for high-precision spectroscopy and tests of fundamental physics. We show that hole transitions can have extremely high sensitivity to alpha-variation due to large relativistic corrections, and propose candidate transitions that have much larger alpha-sensitivities than any previously seen in atomic systems.

physics.atom-ph↗

arXiv2011

Calculation of parity nonconservation in neutral ytterbium

We use configuration interaction and many-body perturbation theory techniques to calculate spin-independent and spin-dependent parts of the parity nonconserving amplitudes of the transitions between the $6s^2 \ ^1$S$_0$ ground state and the $6s5d \ ^3$D$_1$ excited state of $^{171}$Yb and $^{173}$Yb. The results are presented in a form convenient for extracting spin-dependent interaction constants (such as, e.g., anapole moment) from the measurements.

physics.atom-ph↗

arXiv2010

Dynamic polarizabilities and magic wavelengths for dysprosium

We theoretically study dynamic scalar polarizabilities of the ground and select long-lived excited states of dysprosium, a highly magnetic atom recently laser cooled and trapped. We demonstrate that there are a set of magic wavelengths of the unpoarized lattice laser field for each pair of states which includes the ground state and one of these excited states. At these wavelengths, the energy shift due to laser field is the same for both states, which can be useful for resolved sideband cooling on narrow transitions and precision spectroscopy. We present an analytical formula which, near resonances, allows for the determination of approximate values of the magic wavelengths without calculating the dynamic polarizabilities of the excited states.

physics.atom-ph↗

arXiv2010

Atomic transition frequencies, isotope shifts, and sensitivity to variation of the fine structure constant for studies of quasar absorption 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. Recent studies using 140 absorption systems from the Keck telescope and 153 from the Very Large Telescope, suggest that alpha varies spatially. That is, in one direction on the sky alpha seems to have been smaller at the time of absorption, while in the opposite direction it seems to have been larger. To continue this study we need accurate laboratory measurements of atomic transition frequencies. The aim of this paper is to provide a compilation 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 A, and require an accuracy of better than 10^{-4} A. We discuss isotope shift measurements that are needed in order to resolve systematic effects in the study. The coefficients of sensitivity to alpha-variation (q) are also presented.

astro-ph.CO↗