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1. Fine and hyperfine interactions of PbF studied by laser-induced fluorescence spectroscopy

   https://doi.org/https://doi.org/10.1063/5.0099716  

   Chengcheng Zhu, Hailing Wang (January 2022, The Journal of chemical physics)

   The fine and hyperfine interactions in PbF have been studied using the laser-induced fluorescence (LIF) spectroscopy method. Cold PbF molecular beam was produced by laser-ablating a Pb rod under jet-cooled conditions, followed by the reaction with SF6. The LIF excitation spectrum of the (0, 0) band in the B2Σ+–X2Π1/2 system of the 208PbF, 207PbF, and 206PbF isotopologues has been recorded with rotational, fine structure, and hyperfine-structure resolution. Transitions in the LIF spectrum were assigned and combined with the previous X2Π3/2–X2Π1/2 emission spectrum in the near-infrared region [Ziebarth et al., J. Mol. Spectrosc. 191, 108–116 (1998)] and the X2Π1/2 state pure rotational spectrum of PbF [Mawhorter et al., Phys. Rev. A 84, 022508 (2011)] in a global fit to derive the rotational, spin–orbit, spin–rotation, and hyperfine interaction parameters of the ground (X2Π1/2) and the excited (B2Σ+) electronic states. Molecular constants determined in the present work are compared with previously reported values. Particularly, the significance of the hyperfine parameters, A⊥ and A‖, of 207Pb is discussed. 

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2. Measurement of the H3∆₁ Radiative Lifetime in ThO

   Ang, D.G.; Meisenhelder, C.; Panda, C.D.; Wu, X; DeMille, D.; Doyle, J.M.; Gabrielse, G. (April 2022, ArXivorg)

   The best limit on the electron electric dipole moment (eEDM) comes from the ACME II experiment [Nature \textbf{562} (2018), 355-360] which probes physics beyond the Standard Model at energy scales well above 1 TeV. ACME II measured the eEDM by monitoring electron spin precession in a cold beam of the metastable H3Δ1 state of thorium monoxide (ThO) molecules, with an observation time τ≈1 ms for each molecule. We report here a new measurement of the lifetime of the ThO (H3Δ1) state, τH=4.2±0.5 ms. Using an apparatus within which τ≈τH will enable a substantial reduction in uncertainty of an eEDM measurement. 

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3. Quantum control of trapped polyatomic molecules for eEDM searches

   https://doi.org/10.1126/science.adg8155  

   Anderegg, Loïc; Vilas, Nathaniel B.; Hallas, Christian; Robichaud, Paige; Jadbabaie, Arian; Doyle, John M.; Hutzler, Nicholas R. (November 2023, Science)

   Ultracold polyatomic molecules are promising candidates for experiments in quantum science and precision searches for physics beyond the Standard Model. A key requirement is the ability to achieve full quantum control over the internal structure of the molecules. In this work, we established coherent control of individual quantum states in calcium monohydroxide (CaOH) and demonstrated a method for searching for the electron electric dipole moment (eEDM). Optically trapped, ultracold CaOH molecules were prepared in a single quantum state, polarized in an electric field, and coherently transferred into an eEDM-sensitive state where an electron spin precession measurement was performed. To extend the coherence time, we used eEDM-sensitive states with tunable, near-zero magnetic field sensitivity. Our results establish a path for eEDM searches with trapped polyatomic molecules. 

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4. Technique for a direct measurement of the cesium anapole moment using coherent rf and Raman interactions

   https://doi.org/10.1103/PhysRevA.109.032810  

   Damitz, Amy; Quirk, Jonah A; Tanner, Carol E; Elliott, D S (March 2024, Physical Review A)

   We report progress toward measurements of the electric dipole (E1) transition moments between hyperfine components of the ground state of atomic cesium. This transition is weakly E1 allowed due to weak interactions between nucleons within the nucleus, which lead to a parity-odd current distribution and its associated anapole moment. In this report, we discuss the experimental geometry of our measurement scheme, explore the effects of extraneous fields that can obscure the signal, present initial measurements, analyze the sources and magnitudes of measurement noise, and suggest improvements to the current apparatus. 

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5. An improved bound on the electron’s electric dipole moment

   https://doi.org/10.1126/science.adg4084  

   Roussy, Tanya S; Caldwell, Luke; Wright, Trevor; Cairncross, William B; Shagam, Yuval; Ng, Kia Boon; Schlossberger, Noah; Park, Sun Yool; Wang, Anzhou; Ye, Jun; et al (July 2023, Science)

   The imbalance of matter and antimatter in our Universe provides compelling motivation to search for undiscovered particles that violate charge-parity symmetry. Interactions with vacuum fluctuations of the fields associated with these new particles will induce an electric dipole moment of the electron (eEDM). We present the most precise measurement yet of the eEDM using electrons confined inside molecular ions, subjected to a huge intramolecular electric field, and evolving coherently for up to 3 seconds. Our result is consistent with zero and improves on the previous best upper bound by a factor of ~2.4. Our results provide constraints on broad classes of new physics above ${10}^{13}$electron volts, beyond the direct reach of the current particle colliders or those likely to be available in the coming decades. 

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