Calculated and measured values (the latter with uncertainty) of the electron affinity of tin eA(Sn)
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Table 1. Calculated and measured values (the latter with uncertainty) of the electron affinity of tin eA(Sn). Laser photodetachment electron spectrometry (LPES), limited to a few meV precision, was superseded by direct LPT measurement before electron spectrometry came back in its interferometric form, laser photodetachment microscopy (LPM). The first tabulated measurement (Feldmann et al 1977) had been performed by PT spectroscopy with a conventional light source.
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.