Towards state selective ionization for NEPTUNE

The NEPTUNE experiment aims to probe parity-violating, electroweak nuclear properties in molecules using a Penning trap [1]. Close spacings between opposite parity states in molecules strongly enhance weak interaction effects compared to atoms. Moreover, the strong magnetic field of the trap causes the parity states to undergo Zeeman shifts toward near degeneracy [2]. As a result, we expect weak-interaction-induced mixing to be enhanced by more than twelve orders of magnitude relative to atomic systems. This novel technique has the potential to open a new avenue for parity-violation measurements in molecular systems. One challenge is to prepare a single molecule in a desired quantum state that is expected to be sensitive to electroweak interactions. In our first measurement case, this desired quantum state is one of the four hyperfine levels of the electronic and rovibrational ground state of SiO⁺. In this contribution, we will discuss the current status, plans, and ongoing effort toward the state-selective ionization of SiO for the NEPTUNE experiment.

[1] Karthein, J. et al. Phys. Rev. Lett. 133, 033003 (2024)

[2] Altuntas, E. et al. Phys. Rev. Lett. 120, 142501 (2018)