The existence of an autodetaching state of ${\mathrm{O}}^{-}$ with a lifetime on the scale of 100 ns is demonstrated both experimentally and theoretically. The ${\mathrm{O}}^{-}$ lifetime values are determined using two recently developed methods. The experimental approach is based on a derivation from measured electron-loss cross sections combined with time-of-flight spectrometry. For the theoretical approach, the continued Green's function within the formalism of Fano-Feshbach is applied. We present the measured lifetime value of $100\pm 10\text{ns}$. The calculated lifetime value is 75 ns, and is associated with the ($2p^{3}3s^2){}^{4}S$ state of ${\mathrm{O}}^{-}$. We discuss how the existence of a 100-ns-lifetime oxygen metastable anion can impact the modeling of oxygen-containing systems.

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• Atomic & molecular collisions
• Atomic & molecular structure
• Scattering theory
• Ions