The electron affinities of O, Si, and S revisited with the photodetachment microscope

Photodetachment microscopy has been performed on a beam of $^{32}{\rm S}^-$ ions. Analysing the electron images obtained, we find that the electron affinity measurements performed with the photodetachment microscope contain a small bias, due to the difference between the actual and assumed values of the applied electric field. Having a measure of this bias, we can reanalyse older data recorded on the negative ions O- and Si- along similar lines. As a consequence, the values of the electron affinities of Oxygen, Silicon and Sulfur can be given with an improved accuracy. The recommended values (with expanded uncertainties) are now $11\,784.676(7)\,{\rm cm}^{-1}$ for 16O, $11\,207.246(8)\,{\rm cm}^{-1}$ for 28Si, and $16\,752.974(5)\,{\rm cm}^{-1}$ for 32S, i.e. 1.461 113 5(12), 1.389 521 3(13) and 2.077 104 0(9) eV, respectively