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A. Derevianko

Publications and source records attributed to A. Derevianko.

At least 55 records · Page 3Linked to original sources
arXiv2009

Mapping out atom-wall interaction with atomic clocks

We explore a feasibility of measuring atom-wall interaction using atomic clocks based on atoms trapped in engineered optical lattices. Optical lattice is normal to the wall. By monitoring the wall-induced clock shift at individual wells of the lattice, one would measure a dependence of the atom-wall interaction on the atom-wall separation. We rigorously evaluate the relevant clock shifts and show that the proposed scheme may uniquely probe the long-range atom-wall interaction in all three qualitatively-distinct regimes of the interaction: van der Waals (image-charge interaction), Casimir-Polder (QED vacuum fluctuations) and Lifshitz (thermal bath fluctuations). The analysis is carried out for atoms Mg, Ca, Sr, Cd, Zn, and Hg, with a particular emphasis on Sr clock.

physics.atom-ph↗
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

Precision determination of electroweak coupling from atomic parity violation and implications for particle physics

We carry out high-precision calculation of parity violation in cesium atom, reducing theoretical uncertainty by a factor of two compared to previous evaluations. We combine previous measurements with our calculations and extract the weak charge of the 133Cs nucleus, Q_W = -73.16(29)_exp(20)_th. The result is in agreement with the Standard Model (SM) of elementary particles. This is the most accurate to-date test of the low-energy electroweak sector of the SM. In combination with the results of high-energy collider experiments, we confirm the energy-dependence (or "running") of the electroweak force over an energy range spanning four orders of magnitude (from ~10 MeV to ~100 GeV). Additionally, our result places constraints on a variety of new physics scenarios beyond the SM. In particular, we increase the lower limit on the masses of extra $Z$-bosons predicted by models of grand unification and string theories.

hep-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

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

Second-order effects on the hyperfine structure of $P$ states of alkali-metal atoms

We analyze second-order $M1$-$M1$ and $M1$-$E2$ effects to the hyperfine structure (HFS) of the lowest energy $P$ states of alkali-metal atoms arising from the coupling of the two ($J=1/2,3/2$) fine-structure levels through the hyperfine interaction. We find these effects to be especially sizable in Li, leading to a $9σ$ correction to the most accurate reported experimental value of the $A(P_{1/2})$ HFS constant of $^7$Li [D. Das and V. Natarajan, J. Phys. B \textbf{41}, 035001 (2008)]. For the remaining alkali-metal systems, the results tabulated within may be referenced as higher precision is sought in experimental determination of the HFS constants.

physics.atom-ph↗
arXiv2008

Application of B-splines to determining eigen-spectrum of Feshbach molecules

The B-spline basis set method is applied to determining the rovibrational eigen-spectrum of diatomic molecules. A particular attention is paid to a challenging numerical task of an accurate and efficient description of the vibrational levels near the dissociation limit (halo-state and Feshbach molecules). Advantages of using B-splines are highlighted by comparing the performance of the method with that of the commonly-used discrete variable representation (DVR) approach. Several model cases, including the Morse potential and realistic potentials with 1/R^3 and 1/R^6 long-range dependence of the internuclear separation are studied. We find that the B-spline method is superior to the DVR approach and it is robust enough to properly describe the Feshbach molecules. The developed numerical method is applied to studying the universal relation of the energy of the last bound state to the scattering length. We numerically illustrate the validity of the quantum-defect-theoretic formulation of such a relation for a 1/R^6 potential.

physics.atom-ph↗
arXiv2008

Convergence of all-order many-body methods: coupled-cluster study for Li

We present and analyze results of the relativistic coupled-cluster calculation of energies, hyperfine constants, and dipole matrix elements for the $2s$, $2p_{1/2}$, and $2p_{3/2}$ states of Li atom. The calculations are complete through the fourth order of many-body perturbation theory for energies and through the fifth order for matrix elements and subsume certain chains of diagrams in all orders. A nearly complete many-body calculation allows us to draw conclusions on the convergence pattern of the coupled-cluster method. Our analysis suggests that the high-order many-body contributions to energies and matrix elements scale proportionally and provides a quantitative ground for semi-empirical fits of {\em ab inito} matrix elements to experimental energies.

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↗
arXiv2008

Dispelling the curse of the neutron skin in atomic parity violation

We perform calculations for the neutron skin of nuclei and its contribution to atomic parity non-conservation (PNC) in many isotopes of Cs, Ba, Sm, Dy, Yb, Tl, Pb, Bi, Fr, Ra. Three problems are addressed: i) Neutron-skin induced errors to single-isotope PNC, ii) Possibility to measure neutron skin using atomic PNC, iii) Neutron-skin induced errors for ratios of PNC effects in different isotopes. In the latter case the correlations in the neutron skin values for different isotopes lead to cancelations of the errors; this makes the isotopic ratio method a competitive tool in a search for new physics beyond the standard model.

hep-ph↗
arXiv2008

Hyperfine structure of the metastable 3P2 state of alkaline earth atoms as an accurate probe of nuclear magnetic octupole moments

Measuring the hyperfine structure (HFS) of long-lived $^3P_2$ states of divalent atoms may offer the opportunity of extracting relatively unexplored nuclear magnetic octupole and electric hexadecapole moments. Here, using relativistic many-body methods of atomic structure and the nuclear shell model, we evaluate the effect of these higher nuclear moments on the hyperfine structure. We find that the sensitivity of HFS interval measurements in $^{87}$Sr needed to reveal the perturbation caused by the nuclear octupole moment is on the order of kHz. Results of similar analyses for $^{9}$Be, $^{25}$Mg, and $^{43}$Ca are also reported.

physics.atom-ph↗
arXiv2007

Trapping of Neutral Mercury Atoms and Prospects for Optical Lattice Clocks

We report a vapor-cell magneto-optical trapping of Hg isotopes on the ${}^1S_0-{}^3P_1$ intercombination transition. Six abundant isotopes, including four bosons and two fermions, were trapped. Hg is the heaviest non-radioactive atom trapped so far, which enables sensitive atomic searches for ``new physics'' beyond the standard model. We propose an accurate optical lattice clock based on Hg and evaluate its systematic accuracy to be better than $10^{-18}$. Highly accurate and stable Hg-based clocks will provide a new avenue for the research of optical lattice clocks and the time variation of the fine-structure constant.

physics.atom-ph↗
arXiv2006

High-accuracy calculation of black-body radiation shift in $^{133}$Cs primary frequency standard

Black-body radiation (BBR) shift is an important systematic correction for the atomic frequency standards realizing the SI unit of time. Presently, there is a controversy over the value of the BBR shift for the primary $^{133}$Cs standard. At room temperatures the values from various groups differ at $3 \times 10^{-15}$ level, while the modern clocks are aiming at $10^{-16}$ accuracies. We carry out high-precision relativistic many-body calculations of the BBR shift. For the BBR coefficient $β$ at $T=300K$ we obtain $β=-(1.708\pm0.006) \times 10^{-14}$, implying $6 \times 10^{-17}$ fractional uncertainty. While in accord with the most accurate measurement, our 0.35%-accurate value is in a substantial, 10%, disagreement with recent semi-empirical calculations. We identify an oversight in those calculations.

physics.atom-ph↗
arXiv2001

High-precision calculations of electric-dipole amplitudes for transitions between low-lying levels of Mg, Ca, and Sr

To support efforts on cooling and trapping of alkaline-earth atoms and designs of atomic clocks, we performed ab initio relativistic many-body calculations of electric-dipole transition amplitudes between low-lying states of Mg, Ca, and Sr. In particular, we report amplitudes for ^1P_1 --> ^1S_0, ^3S_1, ^1D_2$, for ^3P_1 --> ^1S_0, ^1D_2, and for ^3P_2 --> ^1D_2 transitions. For Ca, the reduced matrix element <4s4p, ^1P_1 ||D|| 4s^2, ^1S_0> is in a good agreement with a high-precision experimental value deduced from photoassociation spectroscopy [Zinner et al., Phys.Rev.Lett., v.85, 2292 (2000)]. An estimated uncertainty of the calculated lifetime of the (3s3p ^1P_1) state of Mg is a factor of three smaller than that of the most accurate experiment. Calculated binding energies reproduce experimental values within 0.1-0.2%.

physics.atom-ph↗
arXiv2000

Reconciliation of the Measurement of Parity-Nonconservation in Cs with the Standard Model

Contributions from the Breit interaction in atomic-structure calculations account for 1.3sigma of the previously reported 2.5sigma deviation from the Standard Model in the 133Cs weak charge [S.C. Bennett and C.E. Wieman, Phys. Rev. Lett. 82, 2484 (1999)]. The updated corrections for the neutron distribution reduce the discrepancy further to 1.0sigma. The updated value of the weak charge is Q_W(133Cs) = -72.65(28)_{expt}(34)_{theor}. The present analysis is a higher-order extension of previous calculation [A. Derevianko, E-print physics/0001046].

hep-ph↗
arXiv2000

Long-range interaction of two metastable rare-gas atoms

We present semiempirical calculations of long-range van der Waals interactions for two interacting metastable rare-gas atoms Ne through Xe. Dispersion coefficients $C_6$ are obtained for homonuclear molecular potentials asymptotically connecting to the $ns(3/2)_{2} + ns(3/2)_{2}$ atomic states. The estimated uncertainty of the calculated $C_6$ dispersion coefficients is 4%.

physics.atom-ph↗