Atomic Electric Dipole Moment Research Articles

Frequency characteristics of nuclear spin oscillator with an artificial feedback toward search for 129Xe atomic electric dipole moment

A 129Xe nuclear spin oscillator with an artificial feedback was constructed, and detailed studies were conducted on its performance, focusing on the frequency stability. As a result, the major sources of drift of the precession frequency in the present spin oscillator setup were identified to be drifts of a solenoid current and an environmental magnetic field. By introducing stabilization systems for the current and the environmental field, which yielded improvements by one order of magnitude on the solenoid current and by a factor of three on the environmental field, a frequency precision of 7.9 nHz was obtained for a one-shot measurement of 3 × 104 s duration. We found, however, that the Allan deviation leveled off at around 30 μHz, indicating a strong need for the precision monitor of the experimental conditions represented by magnetometry. The frequency stability of the spin oscillator is discussed in relation to an experimental search for an electric dipole moment of the 129Xe atom.

Standard model contribution to the electric dipole moment of the deuteron, 3H, and 3He nuclei

We calculate for the first time the electric dipole moment (EDM) of the deuteron, 3H, and 3He nuclei generated by the one-meson exchange CP-odd nuclear force in the standard model. The effective |ΔS| = 1 four-quark operators are matched to the |ΔS| = 1 standard model processes involving the CP phase of the Cabibbo-Kobayashi-Maskawa matrix at the electroweak scale and run down to the hadronic scale μ = 1 GeV according to the renormalization group evolution in the next-to-leading logarithmic order. At the hadronic scale, the hadron matrix elements are modeled in the factorization approach. We then obtain the one-meson (pion, eta meson, and kaon) exchange CP-odd nuclear force, which is the combination of the |ΔS| = 1 meson-baryon vertices which issue from the penguin operator and the hyperon-nucleon transition. From this CP-odd nuclear force, the nuclear EDM is calculated with the realistic Argonne v18 interaction and the CP-odd nuclear force using the Gaussian expansion method. It is found that the EDMs of light nuclear systems are of order O (10−31)e cm. We also estimate the standard model contribution to other hadronic CP violating observables such as the EDMs of 6Li, 9Be nuclei, and the atomic EDMs of 129Xe, 199Hg, 211Rn, and 225Ra generated through the nuclear Schiff moment. We then analyze the source of theoretical uncertainties and show some possible ways to overcome them.

Transportation of a radioactive ion beam for precise laser-trapping experiments.

Francium is the heaviest species among the alkali elements. Due to its properties, francium is said to be of advantage in measurements of tiny observations, such as atomic parity violation and electric dipole moment. Before executing experiments with francium, it must be produced artificially because it is one of the most unstable elements. We produced francium with the nuclear fusion reaction of an oxygen beam and gold target, ionized the produced francium through a thermal ionization process, and extracted the ion with electrostatic fields. However, the thermal ionization process is known to ionize not only an objective atom but also other atomic species. Therefore, a Wien filter was installed to analyze the composition of the ion beam and purify the beam. This allowed us to improve the beam purity from ∼10(-6) to ∼10(-3).

A Database of Force-Field Parameters, Dynamics, and Properties of Antimicrobial Compounds.

We present an on-line database of all-atom force-field parameters and molecular properties of compounds with antimicrobial activity (mostly antibiotics and some beta-lactamase inhibitors). For each compound, we provide the General Amber Force Field parameters for the major species at physiological pH, together with an analysis of properties of interest as extracted from μs-long molecular dynamics simulations in explicit water solution. The properties include number and population of structural clusters, molecular flexibility, hydrophobic and hydrophilic molecular surfaces, the statistics of intra- and inter-molecular H-bonds, as well as structural and dynamical properties of solvent molecules within first and second solvation shells. In addition, the database contains several key molecular parameters, such as energy of the frontier molecular orbitals, vibrational properties, rotational constants, atomic partial charges and electric dipole moment, computed by Density Functional Theory. The present database (to our knowledge the first extensive one including dynamical properties) is part of a wider project aiming to build-up a database containing structural, physico-chemical and dynamical properties of medicinal compounds using different force-field parameters with increasing level of complexity and reliability. The database is freely accessible at http://www.dsf.unica.it/translocation/db/.

Experimental study of electric dipoles on an oxygen-adsorbed Si(100)-2 × 1 surface by non-contact scanning nonlinear dielectric microscopy

Oxygen-adsorption on a Si(100)-2 × 1 surface is investigated by using non-contact scanning nonlinear dielectric microscopy (NC-SNDM). On the Si(100)-2 × 1 surface exposed to oxygen (O2) gas at room temperature, several variations in atomic configuration and electric dipole moment of dimers are observed. Models are proposed for oxygen adsorption which are consistent with the topographies and electric dipole moment distributions obtained by NC-SNDM.

First Measurement of the Atomic Electric Dipole Moment of (225)Ra.

The radioactive radium-225 ((225)Ra) atom is a favorable case to search for a permanent electric dipole moment. Because of its strong nuclear octupole deformation and large atomic mass, (225)Ra is particularly sensitive to interactions in the nuclear medium that violate both time-reversal symmetry and parity. We have developed a cold-atom technique to study the spin precession of (225)Ra atoms held in an optical dipole trap, and demonstrated the principle of this method by completing the first measurement of its atomic electric dipole moment, reaching an upper limit of |d((225)Ra)|<5.0×10(-22) e cm (95% confidence).

Dark forces and atomic electric dipole moments

Postulating the existence of a fnite-mass mediator of T,P-odd coupling between atomic electrons and nucleons we consider its effect on permanent electric dipole moment (EDM) of diamagnetic atoms. We present both numerical and analytical analysis for such mediator-induced EDMs and compare it with EDM results for the conventional contact interaction. Based on this analysis we derive limits on coupling strengths and carrier masses from experimental limits on EDM of 199Hg atom.

Shell model estimate of electric dipole moments in medium and heavy nuclei

Existence of the electric dipole moment (EDM) is deeply related with time-reversal invariance. The EDMof a diamagnetic atom is mainly induced by the nuclear Schiff moment. After carrying out the shell model calculations to obtain wavefunctions for Xe isotopes, we evaluate nuclear Schiff moments for Xe isotopes to estimate their atomic EDMs. We estimate the contribution from each single particle orbital for the Schiff moment. It is found that the contribution on the Schiff moment is very different from orbital to orbital.

Local electric dipole moments for periodic systems via density functional theory embedding.

We describe a novel approach for the calculation of local electric dipole moments for periodic systems. Since the position operator is ill-defined in periodic systems, maximally localized Wannier functions based on the Berry-phase approach are usually employed for the evaluation of local contributions to the total electric dipole moment of the system. We propose an alternative approach: within a subsystem-density functional theory based embedding scheme, subset electric dipole moments are derived without any additional localization procedure, both for hybrid and non-hybrid exchange-correlation functionals. This opens the way to a computationally efficient evaluation of local electric dipole moments in (molecular) periodic systems as well as their rigorous splitting into atomic electric dipole moments. As examples, Infrared spectra of liquid ethylene carbonate and dimethyl carbonate are presented, which are commonly employed as solvents in Lithium ion batteries.

Core-polarization studies of nuclear-Schiff-moment-induced permanent electric dipole moments of atomicXe129,Yb171, andRa225

We have calculated the intrinsic electric dipole moments (EDMs) of $^{129}\mathrm{Xe}$, $^{171}\mathrm{Yb}$, $^{225}\mathrm{Ra}$ atoms induced by the nuclear Schiff moment (NSM). We use the coupled perturbed Hartree-Fock [CPHF] framework to perform this calculation. In this work, the effects of electron correlation on atomic EDMs are studied in CPHF framework by gradual inclusion of virtual orbitals of higher symmetries. Individual orbital contributions to the final magnitude of the EDM are presented. The results for the NSM-induced EDM for these atoms show a trend similar to the electron-nucleon tensor-pseudotensor (T-PT)-induced EDM, the study of which was performed elsewhere. This behavior can be attributed to the fact that the influence of virtual orbitals of higher symmetry on the magnitude of EDM is essentially the same for both T-PT and NSM-induced atomic EDMs. However, we also report in this paper, that the most dominant contribution to the atomic EDM of $^{129}\mathrm{Xe}$, $^{171}\mathrm{Yb}$, $^{225}\mathrm{Ra}$ atoms induced by the NSM arises from the ${s}_{1/2}\text{\ensuremath{-}}{p}_{3/2}$ pairings rather than the ${s}_{1/2}\text{\ensuremath{-}}{p}_{1/2}$ pairings, which were the dominantly contributing pairings for the electron-nucleon tensor-pseudotensor-induced atomic EDM.

Limiting P-odd interactions of cosmic fields with electrons, protons, and neutrons.

We propose methods for extracting limits on the strength of P-odd interactions of pseudoscalar and pseudovector cosmic fields with electrons, protons, and neutrons, by exploiting the static and dynamic parity-nonconserving amplitudes and electric dipole moments they induce in atoms. Candidates for such fields are dark matter (including axions) and dark energy, as well as several more exotic sources described by Lorentz-violating standard model extensions. Atomic calculations are performed for H, Li, Na, K, Rb, Cs, Ba(+), Tl, Dy, Fr, and Ra(+). From these calculations and existing measurements in Dy, Cs, and Tl, we constrain the interaction strengths of the parity-violating static pseudovector cosmic field to be 7 × 10(-15) GeV with an electron, and 3 × 10(-8) GeV with a proton.

Fermion EDMs with minimal flavor violation

We study the electric dipole moments (EDMs) of fermions in the standard model supplemented with right-handed neutrinos and its extension including neutrino seesaw mechanism under the framework of minimal flavor violation (MFV). In the quark sector, we find that the current experimental bound on the neutron EDM does not yield a significant restriction on the scale of MFV. In addition, we consider how MFV may affect the contribution of the strong theta-term to the neutron EDM. For the leptons, the existing EDM data also do not lead to strict limits if neutrinos are Dirac particles. On the other hand, if neutrinos are Majorana in nature, we find that the constraints become substantially stronger. Moreover, the results of the latest search for the electron EDM by the ACME Collaboration are sensitive to the MFV scale of order a few hundred GeV or higher. We also look at constraints from $CP$-violating electron-nucleon interactions that have been probed in atomic and molecular EDM searches.

Multiconfiguration Dirac-Hartree-Fock calculations of atomic electric dipole moments ofRa225,Hg199, andYb171

The multiconfiguration Dirac-Hartree-Fock method is employed to calculate atomic electric dipole moments in the ground states of $^{225}\mathrm{Ra}$, $^{199}\mathrm{Hg}$, and $^{171}\mathrm{Yb}$. For the calculations of the matrix elements we extend the relativistic atomic structure package grasp2k. The extension includes programs to evaluate matrix elements of $\mathcal{P}\mathcal{T}$-odd electron-nucleus tensor-pseudotensor and pseudoscalar-scalar interactions, the atomic electric dipole operator, the nuclear Schiff moment, and the interaction of the electron electric dipole moment with nuclear magnetic moments. The interelectronic interactions are accounted for through valence and core-valence electron correlation effects. The electron shell relaxation is included with separately optimized wave functions of opposite parities.

Multiconfiguration Dirac-Hartree-Fock calculations of EDM for Ra, Hg, Yb

Using multiconfiguration Dirac-Hartree-Fock (MCDHF) method, we calculated the atomic electric dipole moment (EDM) for Ra, Hg, Yb, arising from nuclear Schiff moment, (P,T)-odd electron-nucleon interactions, and interaction of electron EDM with nuclear electromagnetic field.

Axion-induced effects in atoms, molecules, and nuclei: Parity nonconservation, anapole moments, electric dipole moments, and spin-gravity and spin-axion momentum couplings

We show that the interaction of an axion field, or in general a pseudoscalar field, with the axial-vector current generated by an electron through a derivative-type coupling can give rise to a time-dependent mixing of opposite-parity states in atomic and molecular systems. Likewise, the analogous interaction of an axion field with the axial-vector current generated by a nucleon can give rise to time-dependent mixing of opposite-parity states in nuclear systems. This mixing can induce oscillating electric dipole moments, oscillating parity non-conservation effects and oscillating anapole moments in such systems. By adjusting the energy separation between the opposite-parity states of interest to match the axion mass energy, axion-induced experimental observables can be enhanced by many orders of magnitude. Oscillating atomic electric dipole moments can also be generated by axions through hadronic mechanisms, namely the P,T-violating nucleon-nucleon interaction and through the axion-induced electric dipole moments of valence nucleons, which comprise the nuclei. The axion field is modified by the Earth's gravitational field. The interaction of the spin of either an electron or nucleon with this modified axion field leads to axion-induced observable effects. These effects, which are of the form $\mathbf{g} \cdot \mathbf{\sigma}$, differ from the axion-wind effect, which has the form $\mathbf{p}_{\textrm{a}} \cdot \mathbf{\sigma}$.

Investigation of the E2 and E3 matrix elements in200Hg using inelastic scattering

A nuclear structure campaign has been initiated to investigate the isotopes of mercury near A = 199. Currently 199 Hg provides the most stringent limit on an atomic electric dipole moment (EDM). The observation of a permanent EDM would represent a clear signal of CP violation from new physics beyond the Standard Model. Theoretical calculations for 199 Hg are very di cult and give varied predictions for the excited-state spectrum. Understanding the E2 and E3 strengths in the neighbouring even-even iso- topes of mercury will make it possible to develop a nuclear structure model for the Schi strength based on these matrix elements, and thereby constrain present model predictions of the contribution of octupole collectivity to the Schi moment of the nucleus.

Shell model estimate of electric dipole moments in medium and heavy nuclei

Existence of the electric dipole moment (EDM) is deeply related with time-reversal invariance. The EDMof a diamagnetic atom is mainly induced by the nuclear Schiff moment. After carrying out the shell model calculations to obtain wavefunctions for Xe isotopes, we evaluate nuclear Schiff moments for Xe isotopes to estimate their atomic EDMs. We estimate the contribution from each single particle orbital for the Schiff moment. It is found that the contribution on the Schiff moment is very different from orbital to orbital.

Active nuclear spin maser oscillation with double cell

Uncertainty in the frequency precision of the planned experiment to search for a 129 Xe atomic electric dipole moment is dominated by drifts in the frequency shift due to contact interaction of 129 Xe with polarized Rb valence electrons. In order to suppress the frequency shift, a double-cell geometry has been adopted for the confinement of 129 Xe gas. A new process has been identified to take part in the optical detection of spin pre- cession. The parameters controlling the oscillation of the maser in this new double-cell arrangement were optimized. As a result, the frequency shift has been reduced by a factor of 10 or more from the former single-cell geometry.

Studies of pear-shaped nuclei using accelerated radioactive beams

There is strong circumstantial evidence that certain heavy, unstable atomic nuclei are 'octupole deformed', that is, distorted into a pear shape. This contrasts with the more prevalent rugby-ball shape of nuclei with reflection-symmetric, quadrupole deformations. The elusive octupole deformed nuclei are of importance for nuclear structure theory, and also in searches for physics beyond the standard model; any measurable electric-dipole moment (a signature of the latter) is expected to be amplified in such nuclei. Here we determine electric octupole transition strengths (a direct measure of octupole correlations) for short-lived isotopes of radon and radium. Coulomb excitation experiments were performed using accelerated beams of heavy, radioactive ions. Our data on (220)Rn and (224)Ra show clear evidence for stronger octupole deformation in the latter. The results enable discrimination between differing theoretical approaches to octupole correlations, and help to constrain suitable candidates for experimental studies of atomic electric-dipole moments that might reveal extensions to the standard model.

Nuclear spin maser and experimental search for 129 Xe atomic EDM

The present status of an active spin maser which is being developed for an experimental search for 129Xe atomic electric dipole moment (EDM) is presented. In order to realize the long term stability of maser frequency, systematic effects for the spin maser operation were investigated. The correlations in the maser frequency with the solenoid current, the environmental field and the cell temperature were found. With the solenoid current and environmental field being stabilized and the cell temperature lowered, a frequency precision of 7.9 nHz has been achieved for the maser operation.