Session X05: Memorial Session for Walter Johnson: Fundamental Symmetry Violation Searches with Molecules and Atoms

Radium ions and radium-bearing molecules for precision measurement

We work with radium ions for optical clocks and testing fundamental symmetries. We are developing a radium molecule experiment to set limits on time reversal symmetry violation (TRSV). This symmetry violation is at the crux of two open questions: why does the universe lack antimatter, and why is charge parity symmetry not violated in quantum chromodynamics. Searching for TRSV moments of particles and nuclei is a promising route to addressing these questions. Radium has an octupole deformed nucleus which enhances sensitivity to TRSV, which can be further boosted in a radium-bearing molecule. We'll discuss our advances towards a TRSV measurement, including a long-term source for the short-lived radium-225 (15 d half-life) that has provided radium ions on demand for a year. From an operational perspective there is now nothing extraordinary about working with radium ions.   

Atomic theory in the 21st century: breakthrough advances, new applications, and neural networks

Professor Walter Johnson was an extraordinary person and scientist. He pioneered the development of modern relativistic high-precision atomic theory for studies of fundamental physics and other applications. To honor his legacy, I will explore the remarkable progress in atomic theory over the past two decades, highlighting its numerous applications spurred by enhanced computational capabilities, including the development of atomic clocks, advances in fundamental physics, the study of ultracold atoms and quantum simulations, and contributions to astrophysics. The theory story intertwines with experimental breakthroughs in quantum control and the subsequent improvements in measurement precision. I will review recent developments, including large-scale high-performance computing, the transformation of research codes into widely accessible software, the open sharing of data through a community portal, and the application of machine learning in atomic theory.   

Precision measurement and spectroscopy with molecules containing deformed nuclei

Molecules with heavy, deformed nuclei can amplify the sensitivity of CP-violating physics in the hadronic. We are performing experiments with YbOH, which has a quadrupole-deformed nucleus which enhances the nuclear magnetic quadrupole moment (MQM), and RaOH, which as an octupole-deformed nucleus which enhances the nuclear Schiff moment (NSM). In this talk, I will give an update on the status of these efforts, including production and spectroscopy of RaOH, and coherent control in YbOH.   

Measurement of the highly forbidden M1 transition in 7s-8s transition in francium 211.

Atomic parity violation (APV) in weak interaction provides a pathway to test the Standard Model at a uniquely low momentum scale. We are working towards a test of in radioactive francium at the ISAC radioactive beam facility at TRIUMF. We trap and cool francium atoms in a dual magneto optical trap and perform atomic spectroscopy by driving the highly forbidden 7s-8s transition in francium. The hyperfine interaction and relativistic effects give rise to a very faint M1 transition, which is 13 orders of magnitude weaker than allowed transitions. In a first experiment, we measured the M1 amplitude with an accuracy of better than 10 percent. To drive this transition, we intensify the 506 nm light in the interaction region ≈ 4000-fold using a power buildup cavity. Recently we demonstrated near-unity detection efficiency by driving atoms that have undergone the 7s-8s excitation on a cycling transition up to 5000 times. Overall, we have increased the signal rate more than million-fold. This puts us in terms of statistics in reach of taking APV data. We will present details of this work.   

Magnetic Field Control and Monitoring for the ACME III Electron Electric Dipole Moment Search

Improved control and monitoring over magnetic fields ($B$) directly reduces systematic errors in many precision spectroscopic measurements. In the ACME III search for the electron electric dipole moment (eEDM), This was achieved by mitigating the ambient magnetic field using shields and by applying uniform magnetic fields created by coils. 

We successfully diminished the ambient field by over $10^4$ times using a three-layer mu-metal shield. Our advanced self-shielding coil system was capable of generating a uniform magnetic field necessary for eEDM measurements, while ensuring the mu-metal shields remained non-magnetized across more than a thousand field reversals. Combining both shields and coils, we attained magnetic field control with a precision of 10 µG and maintained gradients below 1 µG/cm within the spin-precession volume of 100 × 4.2 × 4.2 cm³. Furthermore, the coils are capable of offering a flexible combination of magnetic field gradients, aiding in the examination of potential systematic errors.

The monitoring of magnetic fields is achieved with an array of magnetometers. We also use the magnetically sensitive Q state of ThO as an in-situ co-magnetometer. With these upgrades, we aim to minimize systematic errors for ACME III eEDM measurement to a level below the statistical accuracy of $1\times 10^{-31}e\dot cm$. The newly constructed ACME III beamline including these upgrades will be presented.   

System Integration of the ACME III Electron Electric Dipole Moment Search

A measurement of the electric dipole moment of the electron (eEDM) serves as a powerful probe for CP-violating new physics beyond the Standard Model. The ACME experiment is a spin precession experiment using a cryogenic beam of thorium monoxide.

The third generation of ACME, ACME III, introduces several upgrades: an electrostatic lens, a longer precession region, enhanced fluorescent collection optics, and SIPM detectors, which collectively increase statistical sensitivity by an order of magnitude. Together with improved E field and B field control, we aim to sufficiently suppress known sources of systematic error. We report recent progress on the integration of these upgrades into our experiment.   

Progress Towards Precision Measurement in SrOH

Precision measurements in trapped polyatomic molecules can probe Beyond Standard Model (BSM) physics at the PeV scale. The PolyEDM Collaboration is building up an experiment to laser cool and trap SrOH to measure the electric dipole moment of the electron, a signature of new CP-violating physics. Linear polyatomic molecules like SrOH leverage the intrinsic new physics sensitivity of the molecule with the ability to both laser cool the molecules and the presence of bending mode parity doublets for robust rejection of systematic errors. Here we report on progress on Stark and Zeeman spectroscopy of the EDM-sensitive SrOH bending mode.