Measurements of the lifetimes of the 7 ${\mathrm{}}^2$$P_{1/2}^o$ and 7 ${\mathrm{}}^2$$P_{3/2}^o$ excited states of thallium

The lifetimes of the 7 ${\mathrm{}}^2$ $P_{1/2}^o$ and 7 ${\mathrm{}}^2$ $P_{3/2}^o$ states of thallium have been measured for the first time by observing the fluorescence decay following two-photon resonant excitation in an atomic beam. The values obtained for these states are 61.9 and 48.4 ns, respectively, with an uncertainty of 2%. These results are in good quantitative agreement with the calculations of Bardsley and Norcross, which include the effect of core polarizability.