Angular Distribution ofO−from Dissociative Electron Attachment toO2

The angular distribution of ${\mathrm{O}}^{-}$ produced by electron bombardment of ${\mathrm{O}}_2$ has been measured in the electron energy range 5.75-8.40 eV. The results show a strong energy dependence and are consistent with the theory of O'Malley and Taylor if the final $\mathrm{O}_2^{}{}_{}{}^{-}$ repulsive resonance state is assumed to have the symmetry ${}_{}{}^2{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$, and if only the first two allowed partial waves of the incident electron corresponding to $L=1\mathrm{}$ and $L=3\mathrm{}$ contribute. The results indicate that the $L=3\mathrm{}$ term becomes more important as energy increases and thereby demonstrate that the single-term approximation for the angular distribution does not apply for this process.