Laser spectroscopy of the thallium atom based on transitions 6p 1/2 → 6D 3/2 → nF 5/2 (n = 13–24)

Abstract

The energies and quantum defects of Rydberg states nF 5/2 (n = 13–24) of the thallium atom have been studied experimentally. The Rydberg states were excited from the ground state 62 P 1/2 by the two-stage scheme through the intermediate state 62 D 3/2. By using a collimated atomic beam and monochromatic radiation of two narrow-band tunable lasers, we have succeeded in resolving the hyperfine and isotopic structures of the ground state of the thallium atom and in determining the energy positions of the states nF 5/2 accurate to 0.03 cm−1, which exceeds the accuracy achieved in the previous works by more than an order of magnitude. The quantum defect of nF 5/2 states is independent of n within the measurement accuracy and is equal to Δ = 1.0344 ± 0.0008. The ionization potential I p = 49266.55 ± 0.03 cm−1 has been found for the 205Tl isotope from the level 62 P 1/2 (F = 0). The energy of the 62 D 3/2 level measured experimentally relative to the state F = 0 of the 205 isotope amounted to 36118.56 ± 0.02 cm−1.