Precise atomic structure measurements in Pb using vapor-cell and atomic-beam spectroscopy

Recently, we employed a Faraday rotation spectroscopy technique with microradian precision to complete the first ever direct measurement of the forbidden electric quadrupole (E2) transition in Pb at 939 nm [1]. Since then, we have adapted our apparatus to perform Faraday spectroscopy in the blue and near-UV, allowing us to measure transition amplitude ratios of transitions starting from the ground state to those originating from low-lying thermally-excited states. Currently we are completing precision measurements of the 368 nm (6p²) ³P₁ → (6p7s) ³P₀ and the 406 nm (6p²) ³P₂ → (6p7s)³P₁ E1 transition amplitudes using samples in quartz vapor cells at precisely controlled temperatures. The UV Faraday spectroscopy has been facilitated by the use of a new CeF₃ single-crystal Faraday modulator which we have extensively characterized. In related spectroscopy work, and following up on previous work with thallium and indium, we are also pursuing a new measurement of lead (scalar and tensor) polarizability in these same excited-state E1 transitions using our high-flux atomic beam apparatus, high-voltage field plates, and a transverse spectroscopy arrangement. In our current experiment, a stabilized in-beam laser cavity enables ‘pre-pumping’ of ground-state Pb atoms to enhance the metastable ³P₁ state population prior to excitation by the UV laser. Current results will be presented.

[1] - D. L. Maser et al., Phys. Rev. A 100, 052506 (2019)