Progress towards a search for CP-violating nuclear Schiff moments using molecules in solids

Nuclear Schiff moments (NSMs) present a powerful probe into new physics through their connection to CP-symmetry violation. Such symmetry violations are needed to explain the observed baryon asymmetry of the Universe. We are investigating the application of molecular matrix methods[1] to the search for NSMs of pear-shaped nuclei in heavy polar radioactive molecules[2]. Pear-shaped nuclei (i.e. those with both octupole deformations), such as ²²⁵Ra, are expected to have enhanced NSMs[3]. These methods involve trapping polar molecules in a noble gas matrix, which is predicted to lock their orientation relative to the matrix lattice vectors. This contribution focuses on the FRIB-EDM3 instrument, which consists of two main parts.

The frontend will create and mass-separate molecular ions, such as RaF. Electrospray ionization will be used to create the molecular ions, then a series of ion optics will introduce the ions to vacuum and perform mass separation[4].

The backend will neutralize the ions, co-deposit them in a noble gas matrix, and perform molecular hyperfine spectroscopy, which will ultimately enable an NSM search.

We believe that this approach may be an efficient method for creating and trapping radioactive molecules starting from a precursor solution made available by the Isotope Harvesting Program at FRIB. Our initial goal is to quantify and optimize the efficiency of this approach. Eventually we aim to carry out a sensitive search for the NSM of ²²⁵Ra using, for example, RaF molecules in solid argon. We will provide an update on the current status of the instrument as well as calculations relevant to developing an NSM measurement scheme.

[1] A.C. Vutha et al, PRA 98, 032513 (2018).

[1] G. Arrowsmith-Kron et al, (2023), arXiv:2302.02165.

[3] N. Auerbach et al, PRL 76, 4316 (1996).

[4] J. Ballof et al, NIMB 541, 224 (2023).