Electron affinity of tin measured by photodetachment microscopy

A beam of Sn^- ions produced by a caesium sputtering ion source is photodetached in the presence of an electric field, with a single-mode ring Ti:Sa laser. The laser wavelength, about 806 nm, is set just above the excitation threshold of the ³P₂, highest fine-structure sublevel of the ³P ground-term of Sn I. The photoelectron energy is measured by photodetachment microscopy. The measured photodetachment threshold is 1239 711.8 (11) m^-1, from which an improved value of the electron affinity of tin can be deduced: 896 944.7 (13) m^-1 or 1.112 070 (2) eV.