arXiv subjects

U. I. Safronova

Publications and source records attributed to U. I. Safronova.

At least 19 recordsLinked to original sources

arXiv2020

Magic Wavelengths of the Yb $6s^2{}\,^1S_0-6s6p\,{}^3P_1$ Intercombination Transition

We calculate and measure the magic wavelengths for the $6s^2{}\,^1S_0-6s6p\,{}^3P_1$ intercombination transition of the neutral ytterbium atom. The calculation is performed with the \textit{ab initio} configuration interaction (CI) + all-order method. The measurement is done with laser spectroscopy on cold atoms in an optical dipole trap. The magic wavelengths are determined to be 1035.68(4) nm for the $π$ transition ($Δm = 0$) and 1036.12(3) nm for the $σ$ transitions ($|Δm| = 1$) in agreement with the calculated values. Laser cooling on the narrow intercombination transition could achieve better results for atoms in an optical dipole trap when the trap wavelength is tuned to near the magic wavelength.

physics.atom-ph↗

arXiv2020

Optical clocks based on the Cf$^{15+}$ and Cf$^{17+}$ ions

Recent experimental progress in cooling, trapping, and quantum logic spectroscopy of highly-charged ions (HCIs) made HCIs accessible for high resolution spectroscopy and precision fundamental studies. Based on these achievements, we explore a possibility to develop optical clocks using transitions between the ground and a low-lying excited state in the Cf$^{15+}$ and Cf$^{17+}$ ions. Using a high-accuracy relativistic method of calculation we predicted the wavelengths of clock transitions, calculated relevant atomic properties, and analyzed a number of systematic effects (such as the electric quadrupole-, micromotion-, and quadratic Zeeman shifts of the clock transitions) that affect the accuracy and stability of the optical clocks. We also calculated magnetic dipole hyperfine-structure constants of the clock states and the blackbody radiation shifts of the clock transitions.

physics.atom-ph↗

arXiv2019

Clock-related properties of Lu+

The singly-ionized lutetium has a number of fortuitous properties well suited for a design of an optical clock and corresponding applications. In this work, we study Lu+ properties relevant to a development of the clock using the relativistic high-precision method combining configuration interaction and the linearized coupled-cluster approaches. The systematic effects due to interaction of an external electric-field gradient with the quadrupole moment and the dynamic correction to the blackbody radiation shift are studied and uncertainties are estimated. The value of the 5d6s 1D_2 polarizability is predicted. We also demonstrate that Lu+ is a good candidate to search for variation of the fine-structure constant.

physics.atom-ph↗

arXiv2018

Nobelium energy levels and hyperfine structure constants

Advances in laser spectroscopy of superheavy ($Z>100$) elements enabled determination of the nuclear moments of the heaviest nuclei, which requires high-precision atomic calculations of the relevant hyperfine structure (HFS) constants. Here, we calculated the HFS constants and energy levels for a number of nobelium (Z=102) states using the hybrid approach, combining linearized coupled-cluster and configuration interaction methods. We also carried out an extensive study of the No energies using 16-electron configuration interaction method to determine the position of the (5f^{13}7s^2 6d) and (5f^{13}7s^2 7p) levels with a hole in the 5f shell to evaluate their potential effect on the hyperfine structure calculations of the low-lying (5f^{14}7s6d) and (5f^{14}7s7p) levels. We find that unlike the case of Yb, the mixing of the low-lying levels with filled and unfilled f shell is small and does not significantly influence their properties. The resulting HFS constants for the 5f^{14}7s7p 1P1 level, combined with laser-spectroscopy measurement, were used to extract nobelium nuclear properties [S. Raeder et al., Phys. Rev. Lett. 120, 232503 (2018)]

physics.atom-ph↗

arXiv2018

Ultracold anions for high-precision antihydrogen experiments

Experiments with antihydrogen ($\overline{\text{H}}$) for a study of matter--antimatter symmetry and antimatter gravity require ultracold $\overline{\text{H}}$ to reach ultimate precision. A promising path towards anti-atoms much colder than a few kelvin involves the pre-cooling of antiprotons by laser-cooled anions. Due to the weak binding of the valence electron in anions - dominated by polarization and correlation effects - only few candidate systems with suitable transitions exist. We report on a combination of experimental and theoretical studies to fully determine the relevant binding energies, transition rates and branching ratios of the most promising candidate La$^{-}$. Using combined transverse and collinear laser spectroscopy, we determined the resonant frequency of the laser cooling transition to be $ν= 96.592\,713(91)$ THz and its transition rate to be $A = 4.90(50) \times 10^{4}$ s$^{-1}$. Using a novel high-precision theoretical treatment of La$^-$ we calculated yet unmeasured energy levels, transition rates, branching ratios, and lifetimes to complement experimental information on the laser cooling cycle of La$^-$. The new data establish the suitability of La$^-$ for laser cooling and show that the cooling transition is significantly stronger than suggested by a previous theoretical study.

physics.atom-ph↗

arXiv2017

High-precision measurements and theoretical calculations of indium excited-state polarizabilities

We report measurements of the $^{115}$In $7p_{1/2}$ and $7p_{3/2}$ scalar and tensor polarizabilities using two-step diode laser spectroscopy in an atomic beam. The scalar polarizabilities are one to two orders of magnitude larger than for lower lying indium states due to the close proximity of the $7p$ and $6d$ states. For the scalar polarizabilities, we find values (in atomic units) of $1.811(4) \times 10^5$ $a_0^3$ and $2.876(6) \times 10^5$ $a_0^3$ for the $7p_{1/2}$ and $7p_{3/2}$ states respectively. We estimate the smaller tensor polarizability component of the $7p_{3/2}$ state to be $-1.43(18) \times 10^4$ $a_0^3$. These measurements represent the first high-precision benchmarks of transition properties of such high excited states of trivalent atomic systems. We also present new ab initio calculations of these quantities and other In polarizabilities using two high-precision relativistic methods to make a global comparison of the accuracies of the two approaches. The precision of the experiment is sufficient to differentiate between the two theoretical methods as well as to allow precise determination of the indium $7p-6d$ matrix elements. The results obtained in this work are applicable to other heavier and more complicated systems, and provide much needed guidance for the development of even more precise theoretical approaches.

physics.atom-ph↗

arXiv2017

Atomic properties of actinide ions with particle-hole configurations

We study the effects of higher-order electronic correlations in the systems with particle-hole excited states using a relativistic hybrid method that combines configuration interaction and linearized coupled-cluster approaches. We find the configuration interaction part of the calculation sufficiently complete for eight electrons while maintaining good quality of the effective coupled-cluster potential for the core. Excellent agreement with experiment was demonstrated for a test case of La$^{3+}$. We apply our method for homologue actinide ions Th$^{4+}$ and U$^{6+}$ which are of experimental interest due to a puzzle associated with the resonant excitation Stark ionization spectroscopy (RESIS) method. These ions are also of interest to actinide chemistry and this is the first precision calculation of their atomic properties.

physics.atom-ph↗

arXiv2017

Relativistic all-order many-body calculation of energies, wavelengths, and $M1$ and $E2$ transition rates for the $3d^n$ configurations in tungsten ions

Energy levels, wavelengths, magnetic-dipole and electric-quadrupole transition rates between the low-lying states are evaluated for W$^{51+}$ to W$^{54+}$ ions with $3d^n$ (n = 2 to 5) electronic configurations using an approach combining configuration interaction with linearized coupled-cluster single-double method. The QED corrections are directly incorporated into the calculations and their effect is studied in detail. Uncertainties of the calculations are discussed. This first study of such highly charged ions with the present method opens the way for future applications allowing an accurate prediction of properties for a very wide range of highly charged ions aimed at providing precision benchmarks for various applications.

physics.atom-ph↗

arXiv2017

A theoretical study of the g-factor of the 6s6p 3P0 state of mercury

We calculate the g-factor of the 6s6p 3P0 state of 199 and 201 mercury isotopes using a relativistic high-precision all-order method that combines the configuration interaction and the coupled-cluster approaches. Our values $g(199Hg) = -0.9485(49)*10^{-3}$ and $g(201Hg) = -0.3504(18)*10^{-3}$ are in agreement with the experimental measurements within the 0.5% theoretical uncertainty. We also calculate the hyperfine quenching rate of the 6s6p 3P0 state in 199Hg and 201Hg and determine its lifetime to be 1.3 and 1.9 s, respectively.

physics.atom-ph↗

arXiv2017

Forbidden M1 and E2 transitions in monovalent atoms and ions

We carried out a systematic high-precision relativistic study of the forbidden magnetic-dipole and electric-quadrupole transitions in Ca+, Rb, Sr+, Cs, Ba+, Fr, Ra+, Ac2+, and Th3+. This work is motivated by the importance of these transitions for tests of fundamental physics and precision measurements. The relative importance of the relativistic, correlation, Breit correction, and contributions of negative-energy states is investigated. Recommended values of reduced matrix elements are presented together with their uncertainties. The matrix elements and resulting lifetimes are compared with other theoretical values and with experiment where available.

physics.atom-ph↗

arXiv2016

Relativistic many-body calculation of energies, lifetimes, polarizabilities, blackbody radiative shift and hyperfine constants in Lu2+

Energy levels of 30 low-lying states of Lu2+ and allowed electric-dipole matrix elements between these states are evaluated using a relativistic all-order method in which all single, double and partial triple excitations of Dirac-Fock wave functions are included to all orders of perturbation theory. Matrix elements are critically evaluated for their accuracy and recommended values of the matrix elements are given together with uncertainty estimates. Line strengths, transition rates and lifetimes of the metastable 5d(3/2) and 5d(5/2) states are calculated. Recommended values are given for static polarizabilities of the 6s, 5d and 6p states and tensor polarizabilities of the 5d and 6p(3/2) states. Uncertainties of the polarizability values are estimated in all cases. The blackbody radiation shift of the 6s(1/2)-5d(5/2) transition frequency of the Lu2+ ion is calculated with the aid of the recommended scalar polarizabilities of the 6s(1/2) and 5d(5/2) states. Finally, A and B hyperfine constants are determined for states of 175Lu2+ with n <= 9. This work provides recommended values of transition matrix elements, polarizabilities and hyperfine constants of Lu2+, critically evaluated for accuracy, for benchmark tests of high-precision theoretical methodology and planning of future experiments.

physics.atom-ph↗

arXiv2016

Magic wavelengths, matrix elements, polarizabilities, and lifetimes of Cs

Motivated by recent interest in their applications, we report a systematic study of Cs atomic properties calculated by a high-precision relativistic all-order method. Excitation energies, reduced matrix elements, transition rates, and lifetimes are determined for levels with principal quantum numbers $n \leq 12$ and orbital angular momentum quantum numbers $l \leq 3$. Recommended values and estimates of uncertainties are provided for a number of electric-dipole transitions and the electric dipole polarizabilities of the $ns$, $np$, and $nd$ states. We also report a calculation of the electric quadrupole polarizability of the ground state. We display the dynamic polarizabilities of the $6s$ and $7p$ states for optical wavelengths between 1160 nm and 1800 nm and identify corresponding magic wavelengths for the $6s-7p_{1/2}$, $6s-7p_{3/2}$ transitions. The values of relevant matrix elements needed for polarizability calculations at other wavelengths are provided.

physics.atom-ph↗

arXiv2016

Atomic Properties of Lu$^+$

Singly ionised Lutetium has recently been suggested as a potential clock candidate. Here we report a joint experimental and theoretical investigation of \ce{Lu^+}. Measurements relevant to practical clock operation are made and compared to atomic structure calculations. Calculations of scalar and tensor polarizabilities for clock states over a range of wavelengths are also given. These results will be useful for future work with this clock candidate.

physics.atom-ph↗

arXiv2015

Actinide ions for testing the spatial $α-$variation hypothesis

Testing the spatial variation of fine-structure constant $α$ indicated in [Webb et al., Phys. Rev. Lett. 107, 191101 (2011)] with terrestrial laboratory atomic measurements requires at least $\dotα/α\sim 10^{-19}~\textrm{y}^{-1}$ sensitivity. We conduct a systematic search of atomic systems for such a test that have all features of the best optical clock transitions leading to possibility of the frequency measurements with fractional accuracy on the level of $10^{-18}$ or better and have a factor of 100 extra enhancement of $α$-variation in comparisons to experimental frequency ratio measurement accuracy. We identify the pair of actinide Cf$^{15+}$ and Es$^{16+}$ ions as the best system for a test of spatial $α-$variation hypothesis as it satisfies both of these requirements and have sufficiently simple electronic structure to allow for high-precision predictions of all atomic properties required for rapid experimental progress.

physics.atom-ph↗

arXiv2015

Towards a Mg lattice clock: Observation of the $^1S_{0}-$$^3P_{0}$ transition and determination of the magic wavelength

We optically excite the electronic state $3s3p~^3P_{0}$ in $^{24}$Mg atoms, laser-cooled and trapped in a magic-wavelength lattice. An applied magnetic field enhances the coupling of the light to the otherwise strictly forbidden transition. We determine the magic wavelength, the quadratic magnetic Zeeman shift and the transition frequency to be 468.463(207)$\,$nm, -206.6(2.0)$\,$MHz/T$^2$ and 655 058 646 691(101)$\,$kHz, respectively. These are compared with theoretical predictions and results from complementary experiments. We also developed a high-precision relativistic structure model for magnesium, give an improved theoretical value for the blackbody radiation shift and discuss a clock based on bosonic magnesium.

physics.atom-ph↗

arXiv2015

The magic road to precision

We predict a sequence of magic-zero wavelengths for the Sr excited $5s5p~ ^3P_0$ state, and provide a general roadmap for extracting transition matrix elements using precise frequency measurements. We demonstrate that such measurements can serve as a best global benchmark of the spectroscopic accuracy that is required for the development of high-precision predictive methods. These magic-zero wavelengths are also needed for state-selective atom manipulation for implementation of quantum logic operations. We also identify five magic wavelengths of the $5s^2\ ^1S_0 - 5s5p\ ^3P_0$ Sr clock transition between 350 nm and 500 nm which can also serve as precision benchmarks.

physics.atom-ph↗

arXiv2015

Transitions between the $4f$-core-excited states in Ir$^{16+}$, Ir$^{17+}$, and Ir$^{18+}$ ions for clock applications

Iridium ions near $4f$-$5s$ level crossings are the leading candidates for a new type of atomic clocks with a high projected accuracy and a very high sensitivity to the temporal variation of the fine structure constant $α$. To identify spectra of these ions in experiment accurate calculations of the spectra and electromagnetic transition probabilities should be performed. Properties of the $4f$-core-excited states in Ir$^{16+}$, Ir$^{17+}$, and Ir$^{18+}$ ions are evaluated using relativistic many-body perturbation theory and Hartree-Fock-Relativistic method (COWAN code). We evaluate excitation energies, wavelengths, oscillator strengths, and transition rates. Our large-scale calculations includes the following set of configurations: $4f^{14-k}5s^{m}5p^{n}$ with $(k+m+n)$ equal to 3, 2, and 1 for the Ir$^{16+}$, Ir$^{17+}$, and Ir$^{18+}$ ions, respectively. The $5s-5p$ transitions are illustrated by the synthetic spectra in the 180 - 200 Årange. Large contributions of magnetic-dipole transitions to lifetimes of low-lying states in the region below 2.5 Ry are demonstrated.

physics.atom-ph↗

arXiv2015

Magic wavelengths for the $5s-18s$ transition in rubidium

Magic wavelengths, for which there is no differential ac Stark shift for the ground and excited state of the atom, allow trapping of excited Rydberg atoms without broadening the optical transition. This is an important tool for implementing quantum gates and other quantum information protocols with Rydberg atoms, and reliable theoretical methods to find such magic wavelengths are thus extremely useful. We use a high-precision all-order method to calculate magic wavelengths for the $5s-18s$ transition of rubidium, and compare the calculation to experiment by measuring the light shift for atoms held in an optical dipole trap at a range of wavelengths near a calculated magic value.

physics.atom-ph↗