Electron affinity of lead

A beam of Pb^- ions produced by a cesium sputtering ion source is photodetached in the presence of an electric field, inside a linear optical cavity. Amplification of the light flux by the resonant cavity makes it possible to record exploitable photoelectron interferograms, even though the Pb^- current does not exceed a few pA. The laser wavenumber is set either just above the first ³P₁ fine-structure excited threshold of neutral Pb, or above the higher ³P₂ threshold. The photoelectron kinetic energy is deduced from the electron interferograms with a precision high enough to provide a new experimental value of the electron affinity of lead, 8 times more precise and slightly lower than the one measured in 2016: or 0.356 721(2) eV, instead of 287 733(13) m^-1 or 0.356 743(16) eV.