Thallium 7p lifetimes derived from experimental data and ab initio calculations of scalar polarizabilities

Two different theoretical methods have been used to complete a new calculation of polarizability in the thallium 6p_{1/2}, 7s, and 7p_{1/2} states. The predictions of the two methods agree to within 1% for the 6p_{1/2} and 7s states and 2% for 7p_{1/2} state. We find that the theoretical expression for the 6p_{1/2} - 7s transition polarizability difference is dominated (greater than 90% contribution) by mixing of the 7s state with the 7p_{1/2} and 7p_{3/2} states. By comparing the theoretical expression to an existing Stark shift measurement [Doret et al., Phys. Rev. A 66, 052504 (2002)], new, highly-accurate values for the thallium 7p excited-state lifetimes have been extracted. The scalar polarizability of the 7p_{1/2} state is also computed, anticipating an experimental determination of this quantity, which will then enable a high-precision determination of the 6d_{j}-7p_{j^{\prime}} transition rates and provide a benchmark test of the two theoretical approaches in the near future.