Electron Temperature Dependence of Recombination ofO2+andN2+Ions with Electrons

A microwave-afterglow/mass-spectrometer apparatus which employs microwave heating of the electrons is used to determine the recombination coefficients, $\alpha \left({\mathrm{O}}_2^{+}\right)$ and $\alpha \left({\mathrm{N}}_2^{+}\right)$, of mass-identified ions with electrons as a function of electron temperature. From electron-density decay data taken under good "ion-tracking" conditions it is found that $\alpha \left({\mathrm{O}}_2^{+}\right)$ varies as ${T_e}^{-0.70\mathrm{}}$ over the range $300°\mathrm{K}<~T_e<~1200°\mathrm{K}$ [starting from a value (1.95 ± 0.2) × ${10}^{-7\mathrm{}}$ ${\mathrm{cm}}^3$/sec at $T_e=300\mathrm{}°$K] and then varies as ${T_e}^{-0.56\mathrm{}}$ between 1200 and 5000°K. In the nitrogen studies the "ion tracking" of the electron decay is less perfect, but ${\mathrm{N}}_2^{+}$ remains the principal afterglow ion and $\alpha \left({\mathrm{N}}_2^{+}\right)$ is found to vary as ${T_e}^{-0.39\mathrm{}}$ over the entire range $300°\mathrm{K}<~T_e<~5000°\mathrm{K}$, starting from a value (${1.8}_{-0.2\mathrm{}}^{+0.4\mathrm{}}$) × ${10}^{-7\mathrm{}}$ ${\mathrm{cm}}^3$/sec at $T_e=300\mathrm{}°$K. These results are compared with other laboratory determinations, results of theoretical calculations, and values inferred from analyses of ionospheric measurements.