arXiv subjects

U. I. Safronova

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

At least 37 records · Page 2Linked to original sources

arXiv2014

Atomic properties of Cd-like and Sn-like ions for the development of frequency standards and search for the variation of the fine-structure constant

A high-precision relativistic calculations of Cd-like Nd$^{12+}$, Sm$^{14+}$ and Sn-like Pr$^{9+}$, Nd$^{10+}$ atomic properties is carried out using an approach that combines configuration interaction and a linearized coupled-cluster method. These ions have long-lived metastable states with transitions accessible by laser excitations, relatively simple electronic structure, high sensitivity to $α$ variation, and stable isotopes. Breit and QED corrections were included into the calculations. Energies, transition wavelengths, electric- and magnetic-multipole reduced matrix elements, lifetimes, and sensitivity coefficients $q$ and $K$ to the variation of the fine-structure constant $α$ were obtained. A detailed study of uncertainties was performed. Energies for similar Cd-like Ba$^{8+}$, La$^{9+}$, Ce$^{10+}$, Pr$^{11+}$ and Sn-like Ba$^{6+}$ ions were calculated and compared with experiment for further tests of the accuracy.

physics.atom-ph↗

arXiv2014

Relativistic all-order calculations of Th, Th$^{+}$ and Th$^{2+}$ atomic properties

Excitation energies, term designations, and $g$-factors of Th, Th$^{+}$ and Th$^{2+}$ are determined using a relativistic hybrid configuration interaction (CI) + all-order approach that combines configuration interaction and linearized coupled-cluster methods. The results are compared with other theory and experiment where available. We find some "vanishing" $g$-factors, similar to those known in lanthanide spectra. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for Th$^{2+}$. To estimate the uncertainties of our results, we compared our values with the available experimental lifetimes for higher $5f7p\ ^3G_{4}$, $7s7p\ ^3P_{0}$, $7s7p\ ^3P_{1}$, and $6d7p\ ^3F_{4}$ levels of Th$^{2+}$. These calculations provide a benchmark test of the CI+all-order method for heavy systems with several valence electrons and yield recommended values for transition rates and lifetimes of Th$^{2+}$.

physics.atom-ph↗

arXiv2014

Study of highly-charged Ag-like and In-like ions for the development of atomic clocks and search for $α$-variation

We carried out detailed high-precision study of Ag-like Nd$^{13+}$, Sm$^{15+}$ and In-like Ce$^{9+}$, Pr$^{10+}$, Nd$^{11+}$, Sm$^{13+}$, Eu$^{14+}$ highly-charged ions. These ions were identified to be of particular interest to the development of ultra-accurate atomic clocks, search for variation of the fine-structure constant $α$, and quantum information [Safronova et. al. Phys. Rev. Lett. 113, 030801 (2014)]. Relativistic linearized coupled-cluster method was used for Ag-like ion calculations, and a hybrid approach that combines configuration interaction and a variant of the coupled-cluster method was used for the In-like ion calculations. Breit and QED corrections were included. Energies, transition wavelengths, electric-dipole, electric-quadrupole, electric-octupole, magnetic-dipole, magnetic-quadrupole, magnetic-octupole reduced matrix elements, lifetimes, and sensitivity coefficients to $α$-variation were calculated. Detailed study of various contributions was carried out to evaluate uncertainties of the final results. Energies for several similar "reference" ions, where the experimental values are available were calculated and compared with experiment for further tests of the accuracy.

physics.atom-ph↗

arXiv2014

Atomic properties of superheavy elements No, Lr, and Rf

The combination of the configuration interaction method and all-order single-double coupled-cluster technique is used to calculate excitation energies, ionization potentials and static dipole polarizabilities of superheavy elements nobelium, lawrencium and rutherfordium. Breit and quantum electrodynamic corrections are also included. The results for the superheavy elements are compared with earlier calculations where available. Similar calculations for lighter analogs, ytterbium, lutetium, and hafnium are used to study the accuracy of the calculations. The estimated uncertainties of the final results are discussed.

physics.atom-ph↗

arXiv2014

Highly-charged ions for atomic clocks, quantum information, and search for $α$-variation

We propose 10 highly-charged ions as candidates for the development of next generation atomic clocks, quantum information, and search for $α$-variation. They have long-lived metastable states with transition frequencies to the ground state between 170-3000 nm, relatively simple electronic structure, stable isotopes and high sensitivity to $α$-variation (e.g., Sm$^{14+}$, Pr$^{10+}$, Sm$^{13+}$, Nd$^{10+}$). We predict their properties crucial for the experimental exploration and highlight particularly attractive systems for these applications.

physics.atom-ph↗

arXiv2013

Magnetic dipole and electric quadrupole moments of the 229Th nucleus

We calculate the A and B hyperfine constants for the low-lying states of 229Th3+ using a high-precision relativistic all-order approach. By combining these calculations with measurements of the 6d and 5f hyperfine constants [C. J. Campbell et al., Phys. Rev. Lett. 106, 223001 (2011)], we determine the magnetic dipole μ=0.360(7)μ_B and the electric-quadrupole Q=3.11(6) eb moments of the 229Th nucleus. Our value for μis five times more accurate and is 22% smaller than the best previous value μ=0.46(4) μ_B [S. Gerstenkorn et al., J. Phys. (Paris) 35, 483 (1974)], while our value for Q is the same, but 2.5 times more accurate than the 2011 result. A systematic study of hyperfine structure in eight other monovalent atoms supports our claim of 2% level uncertainty for $μ$ and Q in 229Th+3.

physics.atom-ph↗

arXiv2013

Relativistic many-body calculation of energies, oscillator strengths, transition rates, lifetimes, polarizabilities, and quadrupole moment of Fr-like Th IV ion

Atomic properties of the 24 low-lying ns, np, nd, nf, and ng states in Th IV ion are calculated using the high-precision relativistic all-order method where all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Recommended values are provided for a large number of electric-dipole matrix elements, oscillator strengths, transition rates, and lifetimes. Scalar polarizabilities of the ground and six excited states (5f_j, 6d_j, 7p_j, and 7s), and tensor polarizabilities of the 5f_j, 6d_j, 7p_{3/2} states of Th IV are evaluated. The uncertainties of the recommended values are estimated. These calculations provide recommended values critically evaluated for their accuracy for a number of Th IV atomic properties for use in theoretical modeling as well as planning and analysis of various experiments including development of ultra precise nuclear clock and RESIS studies of actinide ions

physics.atom-ph↗

arXiv2013

Polarizabilities, Stark shifts, and lifetimes of In atom

We evaluate the polarizabilities of the 5p_{1/2}, 6s, 6p_{1/2}, and 6p_{3/2} states of In using two different high-precision relativistic methods: linearized coupled-cluster approach where single, double and partial triple excitations of the Dirac-Fock wave function are included to all orders of perturbation theory and an approach that combines the configuration interaction and the coupled-cluster method. Extensive comparison of the accuracy of these methods is carried out. The uncertainties of all recommended values are evaluated. Our result for the 6s-5p_{1/2} Stark shift is in excellent agreement with the recent measurement [Ranjit et al., arXiv:1302.0821v1]. Combining our calculation with this precision measurement allows us to infer the values of the 6p_{1/2} and 6p_{3/2} lifetimes in In with 0.8% accuracy. Our predictions for the 6p_{3/2} scalar and tensor polarizabilities may be combined with the future measurement of the 6s-6p_{3/2} Stark shift to accurately determine the lifetimes of the 5d_j states.

physics.atom-ph↗

arXiv2013

Laser cooling and trapping of potassium at magic wavelengths

We carry out a systematic study of the static and dynamic polarizabilities of the potassium atom using a first-principles high-precision relativistic all-order method in which all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Recommended values are provided for a large number of electric-dipole matrix elements. Static polarizabilities of the 4s, 4p_j, 5s, 5p_j, and 3d_j states are compared with other theory and experiment where available. We use the results of the polarizability calculations to identify magic wavelengths for the 4s-np transitions for $n = 4, 5$, i.e. those wavelengths for which the two levels have the same ac Stark shifts. These facilitate state-insensitive optical cooling and trapping. The magic wavelengths for the $4s-5p$ transitions are of particular interest for attaining a quantum gas of potassium at high phase-space density. We find 20 such wavelengths in the technically interest region of 1050-1130 nm. Uncertainties of all recommended values are estimated.

physics.atom-ph↗

arXiv2012

Blackbody radiation shift in the Sr optical atomic clock

We evaluated the static and dynamic polarizabilities of the 5s^2 ^1S_0 and 5s5p ^3P_0^o states of Sr using the high-precision relativistic configuration interaction + all-order method. Our calculation explains the discrepancy between the recent experimental 5s^2 ^1S_0 - 5s5p ^3P_0^o dc Stark shift measurement Δα= 247.374(7) a.u. [Middelmann et. al, arXiv:1208.2848 (2012)] and the earlier theoretical result of 261(4) a.u. [Porsev and Derevianko, Phys. Rev. A 74, 020502R (2006)]. Our present value of 247.5 a.u. is in excellent agreement with the experimental result. We also evaluated the dynamic correction to the BBR shift with 1 % uncertainty; -0.1492(16) Hz. The dynamic correction to the BBR shift is unusually large in the case of Sr (7 %) and it enters significantly into the uncertainty budget of the Sr optical lattice clock. We suggest future experiments that could further reduce the present uncertainties.

physics.atom-ph↗

arXiv2012

Magic wavelengths for optical cooling and trapping of lithium

Using first-principles calculations, we identify magic wavelengths for the 2s-2p and 2s-3p transitions in lithium. The ns and np atomic levels have the same ac Stark shifts at the corresponding magic wavelength, which facilitates state-insensitive optical cooling and trapping. Tune-out wavelengths for which the ground-state frequency-dependent polarizability vanishes are also calculated. Differences of these wavelengths between 6Li and 7Li are reported. Our approach uses high-precision, relativistic all-order methods in which all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Recommended values are provided for a large number of Li electric-dipole matrix elements. Static polarizabilities for the 2s, 2p, 3s, 3p, and 3d levels are compared with other theory and experiment where available. Uncertainties of all recommended values are estimated. The magic wavelengths for the uv 2s-3p transition are of particular interest for the production of a quantum gas of lithium [Duarte et al., Phys. Rev. A 84, 061406R (2011)].

physics.atom-ph↗

arXiv2010

Blackbody radiation shift, multipole polarizabilities, oscillator strengths, lifetimes, hyperfine constants, and excitation energies in Ca+

A systematic study of Ca+ atomic properties is carried out using high-precision relativistic all-order method where all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for the levels up to n = 7. Recommended values and estimates of their uncertainties are provided for a large number of electric-dipole transitions. Electric-dipole scalar polarizabilities for the 5s, 6s, 7s, 8s, 4p, 5p, 3d, and 4d states and tensor polarizabilities for the 4p, 5p, 3d, and 4d states in Ca+ are calculated. Methods are developed to accurately treat the contributions from highly-excited states, resulting in significant (factor of 3) improvement in accuracy of the 3d_{5/2} static polarizability value, 31.8(3) a.u., in comparison with the previous calculation [Arora et al., Phys. Rev. A 76, 064501 (2007)]. The blackbody radiation (BBR) shift of the 4s - 3d_{5/2} clock transition in Ca+ is calculated to be 0.381(4) Hz at room temperature, T=300K. Electric-quadrupole 4s -nd and electric-octupole 4s -nf matrix elements are calculated to obtain the ground state multipole E2 and E3 static polarizabilities. The hyperfine constants A are determined for the low-lying levels up to n = 7. The quadratic Stark effect on hyperfine structure levels of 43Ca+ ground state is investigated. These calculations provide recommended values critically evaluated for their accuracy for a number of Ca+ atomic properties for use in planning and analysis of various experiments as well as theoretical modeling.

physics.atom-ph↗

arXiv2010

Blackbody radiation shift in 87Rb frequency standard

The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in 87Rb using the relativistic all-order method and carried out detailed evaluation of the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly-excited states. Our predicted value for the Stark coefficient, k_S=-1.240(4)\times 10^{-10}\text{Hz/(V/m)}^{2} is three times more accurate than the previous calculation [1].

physics.atom-ph↗

arXiv2009

Calculation of parity nonconserving amplitude and other properties of Ra+

We have calculated parity nonconserving 7s - 6d_{3/2} amplitude E_PNC in 223Ra+ using high-precision relativistic all-order method where all single and double excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Detailed study of the uncertainty of the parity nonconserving (PNC) amplitude is carried out; additional calculations are performed to estimate some of the missing correlation corrections. A systematic study of the parity conserving atomic properties, including the calculation of the energies, transition matrix elements, lifetimes, hyperfine constants, quadrupole moments of the 6d states, as well as dipole and quadrupole ground state polarizabilities, is carried out. The results are compared with other theoretical calculations and available experimental values.

physics.atom-ph↗

arXiv2007

High-precision calculations of In I and Sn II atomic properties

We use all-order relativistic many-body perturbation theory to study 5s^2 nl configurations of In I and Sn II. Energies, E1-amplitudes, and hyperfine constants are calculated using all-order method, which accounts for single and double excitations of the Dirac-Fock wave functions.

physics.atom-ph↗

arXiv2007

Excitation energies, polarizabilities, multipole transition rates, and lifetimes of ions along the francium isoelectronic sequence

Relativistic many-body perturbation theory is applied to study properties of ions of the francium isoelectronic sequence. Specifically, energies of the 7s, 7p, 6d, and 5f states of Fr-like ions with nuclear charges Z = 87 - 100 are calculated through third order; reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for 7s - 7p, 7p - 6d, and 6d - 5f electric-dipole transitions; and 7s - 6d, 7s - 5f, and 5f_5/2 - 5f_7/2 multipole matrix elements are evaluated to obtain the lifetimes of low-lying excited states. Moreover, for the ions Z = 87 - 92 calculations are also carried out using the relativistic all-order single-double method, in which single and double excitations of Dirac-Fock wave functions are included to all orders in perturbation theory. With the aid of the SD wave functions, we obtain accurate values of energies, transition rates, oscillator strengths, and the lifetimes of these six ions. Ground state scalar polarizabilities in Fr I, Ra II, Ac III, and Th IV are calculated using relativistic third-order and all-order methods. Ground state scalar polarizabilities for other Fr-like ions are calculated using a relativistic second-order method. These calculations provide a theoretical benchmark for comparison with experiment and theory.

physics.atom-ph↗

arXiv2007

High-precision study of Cs polarizabilities

We present results of the first-principles calculation of Cs dipole static polarizabilities for the Ns (N = 6 - 12), Np_j (N = 6 - 10), and Nd_j (N = 5 - 10) states using the relativistic all-order method. In our implementation of the all-order method, single and double excitations of Dirac-Fock wave functions are included to all orders in perturbation theory. Additional calculations are carried out for the dominant terms and the uncertainties of our final values are estimated for all states. A comprehensive review of the existing theoretical and experimental studies of the Cs polarizabilities is also carried out. Our results are compared with other values where they are available. These calculations provide a theoretical benchmark for a large number of Cs polarizabilities.

physics.atom-ph↗

arXiv2006

Level-crossing spectroscopy of the 7, 9, and 10D_5/2 states of 133Cs and validation of relativistic many-body calculations of the polarizabilities and hyperfine constants

We present an experimental and theoretical investigation of the polarizabilities and hyperfine constants of D_J states in 133Cs for J=3/2 and J=5/2. New experimental values for the hyperfine constant A are obtained from level-crossing signals of the (7,9,10)D_5/2 states of 133Cs and precise calculations of the tensor polarizabilities alpha_2. The results of relativistic many-body calculations for scalar and tensor polarizabilities of the (5-10)D_3/2 and (5-10)D_5/2 states are presented and compared with measured values from the literature. Calculated values of the hyperfine constants A for these states are also presented and checked for consistency with experimental values.

physics.atom-ph↗