Electron attachment to ${\mathrm{O}}_2$ has been studied for ${\mathrm{O}}_2$-${\mathrm{N}}_2$ and ${\mathrm{O}}_2$-${\mathrm{C}}_2$${\mathrm{H}}_4$ mixtures over a wide range of pressures and electric fields. It was found that $\alpha$, the probability of capture per cm and per mm Hg of ${\mathrm{O}}_2$, depends on the partial pressures of both gases in the ${\mathrm{O}}_2$-${\mathrm{N}}_2$ mixture but only on the ${\mathrm{C}}_2$${\mathrm{H}}_4$ pressure in the ${\mathrm{O}}_2$-${\mathrm{C}}_2$${\mathrm{H}}_4$ mixture. The data have been interpreted in terms of an extension of the mechanism postulated by Bloch and Bradbury, and by Bates and Massey, which involves first the formation of ${\mathrm{O}}_2^{-*}$ (excited ${\mathrm{O}}_2^{-}$) with subsequent collisional stabilization. On this basis estimates were made of the cross section for stabilization of ${\mathrm{O}}_2^{-*}$ by collisions with various kinds of molecules.

• Received 27 October 1958

DOI:https://doi.org/10.1103/PhysRev.114.116