Centrifugal correction to hyperfine structure constants in the ground state of lead monofluoride

The sensitivity of the PbF molecule to the electron electric dipole moment has motivated detailed microwave spectroscopy. Previous theoretical approaches cannot fully explain the spectra. In turn, the explanation from “first principles” is very important both for molecular theory and for confirmation of the correctness of the interpretation of experimental data obtained with high precision. All of these issues are decisively addressed here. We have determined centrifugal correction parameters for hyperfine structure constants, both on lead and fluorine nuclei, of the $X{}^2{\Pi }_{1/2}$ state of lead monofluoride. These parameters were obtained by fitting experimentally observed pure rotational transitions and from ab initio calculations. We show that taking this correction into account is required to reproduce the experimental transition energies obtained by R. J. Mawhorter et al. [Phys. Rev. A 84, 022508 (2011)].