Level scheme of the Sn/Sn− system
Figure 1. Level scheme of the Sn/Sn− system. eA labels the ground-to-ground detachment transition that defines the electron affinity; 'measured' labels the transition measured in this study. The 2D levels of Sn−, which do not play any role in this work, were observed by Scheer et al (1998).
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.