Spectroscopic Predictions for Radioactive ²⁰⁵PbF

The 3 spin ½ particles in ²⁰⁷PbF (both nuclei and the unpaired electron) combine to produce the near-degeneracy of two levels of opposite parity, as verified by Fourier transform microwave (FTMW) spectroscopy [1]. The science state is the ²Π_1/2 ground state, which is inherently less sensitive to stray magnetic fields, making it an ideal candidate for the study of charge-parity non-conservation effects such as the anapole moment [2] as well as the variation of fundamental constants [3]. Furthermore, both theoretical and experimental work indicate that the finely split ²⁰⁷PbF +/– parity levels grow monotonically closer for higher vibrational states [4]. The current study explores the further impact on the energy levels of the (mildly) radioactive spin ⁵/₂ Pb nucleus in ²⁰⁵PbF, incorporating scaled ²⁰⁷PbF hyperfine constants and the additional nuclear electric quadrupole splitting eQq. New relativistic quantum chemical coupled cluster calculations [5] yield a quite small preliminary eQq value of –6 MHz in contrast with the significantly larger value of about –188 MHz for the ²Π_3/2 excited state. This could provide a convenient extra handle for further PbF parity studies, and these implications will also be discussed.



¹ R. Mawhorter, et al., Phys. Rev. A 84, 022508 (2011).

² A. Borschevsky, et al., Phys. Rev. A 88, 022125 (2013).

³ V.V. Flambaum, et al., Phys. Rev. A 88, 052124 (2013).

⁴ V.V. Baturo, et al., Phys. Rev. A 104, 012811 (2021).

⁵ L. Visscher, et al., J. Chem. Phys. 105, 8769 (1996).