Measurement of the Electron Affinity of Thallium by Photodetachment Threshold Spectroscopy

The electron affinity of thallium has been measured using tunable laser photodetachment threshold spectroscopy. The relative cross section for neutral atom production following photodetachment from Tl$^{-}$ was measured with a crossed laser--ion beam apparatus over the photon energy range 0.30 -- 0.50 eV. An \textit{s}-wave threshold was observed due to the opening of the Tl$^{-}$ (6\textit{p}$^{2}$ $^{3}$\textit{P}$_{0}$) to Tl (6\textit{p} $^{2}$\textit{P}$_{1/2}$) ground-state to ground-state transition, yielding a preliminary value for the electron affinity of thallium. The electron affinity measured in the present work is compared with previous experimental [1] and theoretical [2] results. \\[4pt] [1] D. L. Carpenter, A. M. Covington, and J. S. Thompson, \textit{Phys. Rev. A} \textbf{61}, 042501 (2000); [2] see for example J. Li, Z. Zhao, M. Andersson, X. Zhang, and C. Chen, \textit{J. Phys. B-At. Mol. Opt. Phys.} \textbf{45}, 165004 (2012).