Development of Offline Francium Sources to search for hadronic CP violation

We are developing an experiment to measure the Nuclear Schiff Moment of ²²¹Fr and ²²³Fr to search for physics beyond the standard model. The nuclei of ²²³Fr (t_1/2 = 5 minutes) and ²²³Fr (t_1/2 = 22 minutes) have static octupole deformation [1] that make them highly sensitive to CP-violating physics. By binding Fr atoms to Ag (silver) atoms using standard bialkali molecule assembly techniques [2], we will assemble strongly ionic FrAg molecules [3] that offer unprecedented sensitivity to hadronic CP violation [4, 5].

To produce sufficient flux of Fr, we are building continuous offline sources fed from the radioactive decay of long-lived parent nuclides: ²²⁷Ac (t_1/2 = 22 years) for ²²³Fr, and/or ²²⁹Th (t_1/2 = 7340 years) for ²²¹Fr. We will use a 700°C oven to extract Fr atoms out of Ac, effusively filter and ionize Fr. Both sources produce Fr⁺ ions, which will be neutralized and the resulting Fr atoms captured in a vapor cell Magneto-Optical Trap (MOT) [6]. We present our plans and designs for testing and realizing these offline francium sources, as well as results from forming a Rb MOT produced by neutralizing a Rb+ ion beam.

[1] Spevak, V., Auerbach, N., & Flambaum, V. V. (1997). PRC 56(3), 1357.

[2] Ni, K-K., et al. (2008) Science. 322(5899).

[3] Śmiałkowski, M., & Tomza, M. (2021). PRA 103(2), 022802.

[4] Fleig, T., & DeMille, D. (2021). NJP 23(11), 113039.

[5] Kłos, J., Li, H., Tiesinga, E., & Kotochigova, S. (2022).NJP, 24(2), 025005.

[6] Tandecki, M., (2013) J. Instrum. 8(12), P12006