High-precision measurements of atomic structure in lead and other multi-valence atomic systems

Recently, we used 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. Comparing its transition amplitude to the magnetic dipole (M1) transition, we found excellent agreement with the theoretical value predicted from new ab initio calculations in Pb¹. Since then, we have developed our apparatus to perform Faraday spectroscopy in the blue and near-UV which compare quantum-mechanical linestrengths between transitions starting from the ground state and 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. We again use the ground-state M1 transition for normalization/comparison, noting that the E1 transitions originate from states whose small Boltzmann population almost exactly compensate for the intrinsic E1/M1 linestrength differences. In parallel work, and following up on previous work with thallium and indium², we are also pursuing new measurements of lead polarizability using our high-flux atomic beam apparatus, high-voltage field plates, and a transverse Faraday rotation spectroscopy arrangement. We plan to extend both sets of measurements in Pb to other multi-valence atomic systems such as thallium and barium, providing further new benchmark tests of state-of-the-art atomic structure calculations. Current results will be presented.

¹ D.L. Maser, Eli Hoenig, B.-Y. Wang, P.M. Rupasinghe, S.G. Porsev, M.S. Safronova, and P.K. Majumder, Phys. Rev. A 100, 052506 (2019).

² N.B. Vilas, B.-Y. Wang, P.M. Rupasinghe, D.L. Maser, M.S. Safronova, U.I. Safronova, and P.K. Majumder, Phys. Rev. A 97, 022507 (2018).