Electron affinity of lead
Résumé
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 finestructure 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: eA(Pb) = 287 714.9(1.5) m-1 or 0.356 721(2) eV, instead of 287 733(13) m−1 or 0.356 743(16) eV.