The electron affinity of atomic oxygen, an important calibration standard in negative-ion photoelectron spectroscopy, has been determined by tunable-laser photodetachment in a coaxial laser–ion-beam spectrometer to be 11 784.645±0.006 ${\mathrm{cm}}^{\mathrm{-}1}$. In addition, the spin-orbit splitting between the ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{3/2}^{}{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{1/2}^{}{}_{}{}^{}$ states of ${\mathrm{O}}^{\mathrm{-}}$ was found to be 177.13±0.05 ${\mathrm{cm}}^{\mathrm{-}1}$.

• Received 15 February 1985

DOI:https://doi.org/10.1103/PhysRevA.32.1890