Electron Electric Dipole Research Articles

Optical cycling and sensitivity to the electron's electric dipole moment in gold-containing molecules

Optical cycling and sensitivity to the electron's electric dipole moment in gold-containing molecules

Constraining CP Violating Nucleon-Nucleon Long-Range Interactions in Diatomic eEDM Searches.

The searches for CP violating effects in diatomic molecules, such as HfF^{+} and ThO, are typically interpreted as a probe of the electron's electric dipole moment (eEDM), a new electron-nucleon interaction, and a new electron-electron interaction. However, in the case of a nonvanishing nuclear spin, a new CP violating nucleon-nucleon long-range force will also affect the measurement, providing a new interpretation of the eEDM experimental results. Here, we use the HfF^{+} eEDM search and derive a new bound on this hypothetical interaction, which is the most stringent from terrestrial experiments in the 1eV-10keV mass range. These multiple new physics sources motivate independent searches in different molecular species for CP violation at low energy that result in model independent bounds, which are insensitive to cancellation among them.

Systematic errors arising from polarization imperfections in measurements of the electron's electric dipole moment

Systematic errors arising from polarization imperfections in measurements of the electron's electric dipole moment

Theoretical Investigation of Spectroscopic Properties of the Alkaline-Earth-Metal Monohydrides toward Laser Cooling and Magneto-Optical Trapping.

Alkaline-earth-metal monohydrides MH (M = Be, Mg, Ca, Sr, Ba) have long been regarded as promising candidates toward laser cooling and trapping; however, their rich internal level structures that are amenable to magneto-optical trapping have not been completely explored. Here, we first systematically evaluated Franck-Condon factors of these alkaline-earth-metal monohydrides in the A2Π1/2 ← X2Σ+ transition, exploiting three respective methods (the Morse potential, the closed-form approximation, and the Rydberg-Klein-Rees method). The effective Hamiltonian matrix was introduced for MgH, CaH, SrH, and BaH individually in order to figure out their molecular hyperfine structures of X2Σ+, the transition wavelengths in the vacuum, and hyperfine branching ratios of A2Π1/2(J' = 1/2,+) ← X2Σ+(N = 1,-), followed by possible sideband modulation proposals to address all hyperfine manifolds. Lastly, the Zeeman energy level structures and associated magnetic g factors of the ground state X2Σ+(N = 1,-) were also presented. Our theoretical results here not only shed more light on the molecular spectroscopy of alkaline-earth-metal monohydrides toward laser cooling and magneto-optical trapping but also can contribute to research in molecular collisions involving few-atom molecular systems, spectral analysis in astrophysics and astrochemistry, and even precision measurement of fundamental constants such as the quest for nonzero detection of electron's electric dipole moment.

Data presented in "A new bound on the electron's electric dipole moment"

Data presented in "A new bound on the electron's electric dipole moment"

Spectroscopy on the electron-electric-dipole-moment–sensitive states of ThF+

An excellent candidate molecule for the measurement of the electron's electric dipole moment (eEDM) is thorium monofluoride (ThF$^+$) because the eEDM-sensitive state, $^3\Delta_1$, is the electronic ground state, and thus is immune to decoherence from spontaneous decay. We perform spectroscopy on $X\,^3\Delta_1$ to extract three spectroscopic constants crucial to the eEDM experiment: the hyperfine coupling constant, the molecular frame electric dipole moment, and the magnetic $g$-factor. To understand the impact of thermal blackbody radiation on the vibrational ground state, we study the lifetime of the first excited vibrational manifold of $X\,^3\Delta_1$. We perform ab initio calculations, compare them to our results, and discuss prospects for using ThF$^+$ in a new eEDM experiment at JILA.

New techniques for a measurement of the electron's electric dipole moment

New techniques for a measurement of the electron's electric dipole moment

Second-Scale Coherence Measured at the Quantum Projection Noise Limit with Hundreds of Molecular Ions.

Cold molecules provide an excellent platform for quantum information, cold chemistry, and precision measurement. Certain molecules have enhanced sensitivity to beyond standard model physics, such as the electron's electric dipole moment (eEDM). Molecular ions are easily trappable and are therefore particularly attractive for precision measurements where sensitivity scales with interrogation time. Here, we demonstrate a spin precession measurement with second-scale coherence at the quantum projection noise (QPN) limit with hundreds of trapped molecular ions, chosen for their sensitivity to the eEDM rather than their amenability to state control and readout. Orientation-resolved resonant photodissociation allows us to simultaneously measure two quantum states with opposite eEDM sensitivity, reaching the QPN limit and fully exploiting the high count rate and long coherence.

Probing light top partners with CP violation

We investigate CP-violating effects induced by light top partners in composite Higgs theories. We find that sizable contributions to the dipole moments of the light SM quarks and leptons are generically generated at the two-loop level through Barr-Zee-type diagrams. The present constraints on the electron and neutron electric dipole moments translate into bounds on top partner masses of order few TeV and are competitive with the reach of LHC direct searches. Interestingly, we find that CP-violation effects are sensitive to the same operators that control top partner single production. Near-future improvements in the determination of the electron dipole moment will extend the reach on top partner masses beyond the 5–10TeV range.

Laser Cooled YbF Molecules for Measuring the Electron’s Electric Dipole Moment

We demonstrate one-dimensional sub-Doppler laser cooling of a beam of YbF molecules to 100 μK. This is a key step towards a measurement of the electron's electric dipole moment using ultracold molecules. We compare the effectiveness of magnetically assisted and polarization-gradient sub-Doppler cooling mechanisms. We model the experiment and find good agreement with our data.

Precision Measurement of the Electron's Electric Dipole Moment Using Trapped Molecular Ions.

We describe the first precision measurement of the electron's electric dipole moment (d_{e}) using trapped molecular ions, demonstrating the application of spin interrogation times over 700ms to achieve high sensitivity and stringent rejection of systematic errors. Through electron spin resonance spectroscopy on ^{180}Hf^{19}F^{+} in its metastable ^{3}Δ_{1} electronic state, we obtain d_{e}=(0.9±7.7_{stat}±1.7_{syst})×10^{-29} e cm, resulting in an upper bound of |d_{e}|<1.3×10^{-28} e cm (90%confidence). Our result provides independent confirmation of the current upper bound of |d_{e}|<9.4×10^{-29} e cm [J. Baron et al., New J. Phys. 19, 073029 (2017)NJOPFM1367-263010.1088/1367-2630/aa708e], and offers the potential to improve on this limit in the near future.

The permanent electric dipole moment of gold chloride, AuCl

The [19.20]0+-X1Σ+ (0,0) band system of gold chloride, AuCl, has been studied using optical Stark spectroscopy. The [19.20]0+ state is analysed as a 3Π electronic state, and the observed Stark shifts analysed to determine ground and excited electronic state permanent electric dipole moments, μel. A considerably smaller μel of 0.32 ± 0.17 D for the [19.20]0+ (v = 0) state, in comparison to that of 3.69 ± 0.02D for the X1Σ+ (v = 0) state is observed. The experimental assignment of the [19.20]0+ state to a component of the 3Π state has been corroborated by high-level quantum–chemical calculations using exact two-component theory for treating relativistic effects and the equation-of-motion coupled-cluster approach for describing the electronic excited state. A close inspection of the electronic wave functions for the 3Π states of gold monohalides reveals significant participation of excitations from the halogen valence p orbitals to the anti-bonding molecular orbitals mainly localised on the gold atom. This leads to a charge transfer from halogen to gold and is responsible for the dramatic reduction of dipole moment in the 3Π states in comparison to the ground states as observed in the Stark-shift analysis. It has been further demonstrated that this ligand to metal charge transfer increases along the F to I series and leads to predicted dipole moments in the 3Π states of AuBr and AuI that point towards the gold atoms, qualitatively different than might be anticipated.

Ac Stark effect in ThOH3Δ1for the electron electric-dipole-moment search

A method and code for calculations of diatomic molecules in the external variable electromagnetic field have been developed. Code applied for calculation of systematics in the electron's electric dipole moment search experiment on ThO $H^3\Delta_1$ state related to geometric phases, including dependence on $\Omega$-doublet, rotational level, and external static electric field. It is found that systematics decrease cubically with respect to the frequency of the rotating transverse component of the electric field. Calculation confirms that experiment on ThO $H^3\Delta_1$ state is very robust against systematic errors related to geometric phases.

Stochastic multi-channel lock-in detection

High-precision measurements benefit from lock-in detection of small signals. Here we discuss the extension of lock-in detection to many channels, using mutually orthogonal modulation waveforms, and show how the choice of waveforms affects the information content of the signal. We also consider how well the detection scheme rejects noise, both random and correlated. We address the particular difficulty of rejecting a background drift that makes a reproducible offset in the output signal and we show how a systematic error can be avoided by changing the waveforms between runs and averaging over many runs. These advances made possible a recent measurement of the electron's electric dipole moment (Hudson et al 2011 Nature 473 493).

Design for a fountain of YbF molecules to measure the electron's electric dipole moment

We propose an experiment to measure the electric dipole moment (EDM) of the electron using ultracold YbF molecules. The molecules are produced as a thermal beam by a cryogenic buffer gas source, and brought to rest in an optical molasses that cools them to the Doppler limit or below. The molecular cloud is then thrown upward to form a fountain in which the EDM of the electron is measured. A non-zero result would be unambiguous proof of new elementary particle interactions, beyond the standard model.

Addendum to “Possibility of 0-g-factor paramagnetic molecules for measurement of the electron's electric dipole moment”

Recent experimentation has revealed a discrepancy between the calculated and actual hyperfine structure of the ${}^{207}$Pb${}^{19}$F molecule. This discrepancy has been attributed to a misrepresentation of the parity for the ground-state PbF molecule. In a previously published work [Shafer-Ray, Phys. Rev. A 73, 034102 (2006)], we derived a formula for the electric-field-dependent $g$ factor of the ground-state PbF molecule with the misassigned parity. In this Addendum, we reformulate that work and derive the $g$ factor based on the corrected ground state. We discuss the impact of the corrected $g$ factor of the PbF molecule and conclude that the PbF molecule has a $g$ factor which can be small enough to perform an experiment sensitive to the electron's electric dipole moment.

Measurement of the electron's electric dipole moment using YbF molecules: methods and data analysis

We recently reported a new measurement of the electron's electric dipole moment using YbF molecules (Hudson et al 2011 Nature473 493). Here, we give a more detailed description of the methods used to make this measurement, along with a fuller analysis of the data. We show how our methods isolate the electric dipole moment from imperfections in the experiment that might mimic it. We describe the systematic errors that we discovered, and the small corrections that we made to account for these. By making a set of additional measurements with greatly exaggerated experimental imperfections, we find upper bounds on possible uncorrected systematic errors which we use to determine the systematic uncertainty in the measurement. We also calculate the size of some systematic effects that have been important in previous electric dipole moment measurements, such as the motional magnetic field effect and the geometric phase, and show them to be negligibly small in the present experiment. Our result is consistent with an electric dipole moment of zero, so we provide upper bounds to its size at various confidence levels. Finally, we review the prospects for future improvements in the precision of the experiment.

Designs of biased Stark guides for polar molecules

Here we consider three possible biased electrostatic guides of polar molecules. The design of these guides is motivated by their possible uses in a precision measurement of the electron's electric dipole moment. These guides may also have applications in the alignment-preserving transportation of ultracold molecules.

The electron's electric dipole moment

The electron's electric dipole moment

Investigating the structure-sensitivity relationship of metalloporphyrins based chemical sensors

In this paper a methodology to connect the sensitivity of porphyrins coated quartz microbalances and the porphyrin molecular structure is outlined. Porphyrins can interact with guest molecules with different mechanisms exceding those usually considered in simple partition systems, For this reason in this paper an approach in the frame of the Quantitative Structure Activity Relationship models is proposed. Experiments here illustrated were concerned with an array of porphyrins based sensors differing only for the metal ion. Results show that different metals tend to capture distint physical descriptors of the guest molecule. In particular the set of analyzed porphyrins can be divided in those enhancing the sensitivity to electron donor molecules, electric dipole and molecular size.