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

Photodetachment microscopy has been performed on a beam of 32S- 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 11784.676(7)cm-1 for 16O, 11207.246(8)cm-1 for 28Si, and 16752.974(5)cm-1 for 32S, i.e. 1.461∈113∈5(12), 1. 389∈521∈3(13) and 2.077∈104∈0(9) eV, respectively.