Electron Avalanches in Oxygen: Theory

The continuity equations for electrons and the various negative- and positive-ion species of oxygen (${\mathrm{O}}^{-}$, $\mathrm{O}_2^{}{}_{}{}^{-}$, $\mathrm{O}_3^{}{}_{}{}^{-}$, $\mathrm{O}_4^{}{}_{}{}^{-}$) are solved with the initial conditions and boundary conditions characteristic of electron avalanches in uniform fields. Account is made of the gain and loss reactions such as electron attachment, detachment, charge transfer, and ion conversion, as encountered in avalanches in oxygen over a wide range of pressures, and field strength over pressures (1-100 torr and 30-100 V/cm torr, respectively). Account is also made of the collision history of the velocity-distribution function of the atomic negative ion ${\mathrm{O}}^{-}$. Solutions are given for two cases of interest: first, for a study of the ion component of avalanches, with a time resolution of ∼ 0.5 μsec; second, for a study of the electron component, with a time resolution of ∼ 10 nsec. In this way measurements of "effective" rates of attachment, detachment, charge-transfer, and ion-conversion reactions can be given an interpretation in terms of the basic processes involved.