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Establishing a nonzero measurement of the electron Electric Dipole Moment (eEDM) has long been a fundamental pursuit in atomic, molecular and optical physics, offering possible insights into new physics beyond the Standard Model. In this regard, lead monofluoride (PbF) has emerged as a potential candidate for measuring eEDM primarily due to its suitable properties such as the strong internal effective electric field, and eEDM-sensitive ground state with large Ω-doubling and small magnetic g factor. In the present work, we realized the production of a buffer-gas-cooled PbF molecular beam and characterized its high-resolution spectroscopy in the B 2Σ+(υ’=0) ← X1 2Π1/2(υ = 0) transition, including both direct absorption and laser-induced fluorescence spectroscopy. A highly concentrated beam of PbF molecules is obtained with a central forward velocity of 223 ± 17 m/s, while 81, 66 and 24 hyperfine-structure-resolved spectral lines with a frequency accuracy of 40 MHz have been assigned respectively for 208PbF, 207PbF and 206PbF isotopologues. The hyperfine constants due to the 19F nucleus (A∥ and A⊥) of the B state are reported for the first time, and those of the 207Pb nucleus have been also updated. Such a cryogenic molecular beam of PbF in association with its hyperfine-structure-resolved spectral atlas of the B 2Σ+(υ’=0) ← X1 2Π1/2(υ = 0) transition will be essential in developing sensitive detection schemes towards the eEDM measurement.
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Fine and hyperfine interactions of PbF studied by laser-induced fluorescence spectroscopy
The fine and hyperfine interactions in PbF have been studied using the laser-induced fluorescence (LIF) spectroscopy method. Cold PbF molecular beam was produced by laser-ablating a Pb rod under jet-cooled conditions, followed by the reaction with SF6. The LIF excitation spectrum of the (0, 0) band in the B2Σ+–X2Π1/2 system of the 208PbF, 207PbF, and 206PbF isotopologues has been recorded with rotational, fine structure, and hyperfine-structure resolution. Transitions in the LIF spectrum were assigned and combined with the previous X2Π3/2–X2Π1/2 emission spectrum in the near-infrared region [Ziebarth et al., J. Mol. Spectrosc. 191, 108–116 (1998)] and the X2Π1/2 state pure rotational spectrum of PbF [Mawhorter et al., Phys. Rev. A 84, 022508 (2011)] in a global fit to derive the rotational, spin–orbit, spin–rotation, and hyperfine interaction parameters of the ground (X2Π1/2) and the excited (B2Σ+) electronic states. Molecular constants determined in the present work are compared with previously reported values. Particularly, the significance of the hyperfine parameters, A⊥ and A‖, of 207Pb is discussed.
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- Award ID(s):
- 1955310
- PAR ID:
- 10353103
- Date Published:
- Journal Name:
- The Journal of chemical physics
- Volume:
- 157
- ISSN:
- 1520-9032
- Page Range / eLocation ID:
- 084307
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/https://doi.org/10.1063/5.0099716
