Lifetime and hyperfine structure of the level (6s26d)2D3/2of thallium I

Abstract

The level-crossing technique in resonance fluorescence has been applied to determine the lifetime and hyperfine structure of the level (6s26d)2D3/2 in Tl 1. No distinction was made between the two stable isotopes 203 and 205 since their nuclear moments are identical within the accuracy of these experiments. The results (5 2 ± 0.8) × 10-9 sec for the lifetime, and 42 2 ± 1 8 Mc/s for the hyperfine interaction constant, are in good agreement with the measurements of Gallagher and Lurio. The measured lifetime agrees with a value calculated from measurements of the spontaneous transition probabilities from the excited state, and the measured hyperfine interaction constant agrees with the value calculated from the Goudsmit-Fermi-Segrè theory. This latter agreement is probably fortuitous because the theory does not take into account the effects of configuration interaction, which might in this case be considerable.