ZOMBIES: Towards measuring the parity-violating nuclear anapole moment of ¹³⁷Ba in BaF molecules

The ZOMBIES experiment aims to measure the parity-violating nuclear anapole moment of ¹³⁷Ba in barium monofluoride (BaF) molecules. A proof of principle experiment with the ¹⁹F nucleus in ¹³⁸Ba¹⁹F demonstrated a sensitivity sufficient to measure the predicted effect in ¹³⁷BaF, at the 10% level [1]. Several improvements have since been incorporated into the ZOMBIES system, such as a cryogenic buffer gas molecular beam source, and an improved laser frequency locking scheme. We are in the process of implementing rotational and hyperfine cooling in the ground state of ¹³⁷BaF, along with magnetic focusing of the molecular beam, to greatly increase the useful molecular beam flux. Additionally, we are investigating the Zeeman structure of the A ²Π_1/2 states, as well as the hyperfine and Zeeman structure of the D ²Σ⁺ states of ¹³⁷BaF; both are essential for the state preparation and detection schemes in ZOMBIES. We will present our progress in all these activities.

[1] E. Altuntaş, J. Ammon, S. B. Cahn, and D. DeMille, Demonstration of a sensitive method to measure nuclear-spin-dependent parity violation, Phys. Rev. Lett. 120, 142501 (2018)