The apparent detachment energy at the 3P2 threshold, for mean photoelectron kinetic energies ranging from 33.8 to 70.7 m−1
Figure 3. The apparent detachment energy at the 3P2 threshold, for mean photoelectron kinetic energies ranging from 33.8 to 70.7 m−1. Open circles, triangles and diamonds are data taken at 183, 267 and 364 V m−1, respectively. Extrapolation down to = 0 produces a measurement of the 3P2 PT, 1239 711.8(11) m−1. The continuous line is the linear regression of the data, the nearly zero slope of which reveals that the error on the electric field value was probably lower than 0.5%. Larger error bars for lower electric fields are due to the larger perturbation of electron interferograms by spurious electric fields in the vicinity of the electron detector.
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.