The electron affinities of the primary isotopes of lead have been precisely measured using photodetachment threshold spectroscopy. The relative cross sections for photodetachment from ${\mathrm{Pb}}^{-}$ isotopes 206, 207, and 208 were observed using a tunable midinfrared optical parametric oscillator-amplifier to determine the ground-state binding energies. The isotope-averaged electron affinity of Pb was measured to be 356.723(7) meV, in excellent agreement with previous measurements. Furthermore, the isotope shifts in the electron affinities were determined to be $-0.003$(4) meV for ${}^{206}\mathrm{Pb}{}^{208}\mathrm{Pb}$ and $-0.002$(4) meV for ${}^{207}\mathrm{Pb}{}^{208}\mathrm{Pb}$, providing insight to resolve previous discrepancies regarding the magnitude of these shifts.

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• Electronic structure of atoms & molecules
• Photodetachment