Two Autodetaching States ofO−

Two autodetaching states of ${\mathrm{O}}^{-}$ have been found by observing the electron energy spectrum of ${\mathrm{O}}^{-}$ ions excited in collisions with a He target at keV beam energies. The energies of the states have been measured as 10. 112 and 12. 115 ± 0. 010 eV. The ${\mathrm{H}}^{-}$ ${}_{}{}^1{}_{}{}^{}S$, ${}_{}{}^3{}_{}{}^{}P$, and ${}_{}{}^1{}_{}{}^{}D$ autodetaching states below the $n=2\mathrm{}$ hydrogen level are excited in ${\mathrm{O}}^{-}$ on ${\mathrm{H}}_2$ collisions, and the ${\mathrm{Ar}}^{-}$ autodetaching states below the first excited argon level are formed in ${\mathrm{O}}^{-}$ on Ar collisions. No structure in the electron energy spectrum was seen for collisions of ${\mathrm{O}}^{-}$ on ${\mathrm{O}}_2$ or Ne.