Dissociative recombination and excitation of O2+: Cross sections, product yields and implications for studies of ionospheric airglows

We present experimental data on the dissociative recombination (DR) and the dissociative excitation (DE) of ${\mathrm{O}}_{\mathrm{2}}^{\mathrm{+}}$ in its electronic and vibrational ground state using a heavy ion storage ring. The absolute DR cross section has been determined over an electron collision energy range from 1 meV to 3 eV. The thermal DR rate coefficient is derived; ${\mathrm{\alpha (T}}_e{\text{)=2.4×10}}^{\text{−7}}{\text{(300/T}}_e{)}^{\text{0.70±0.01}} {\mathrm{cm}}^{\mathrm{3}}{\mathrm{ s}}^{\mathrm{-1}},$ for $\text{T>200\hspace{0.05em}}\mathrm{K}.$ The threshold for DE was observed near its energetic threshold of 6.7 eV. The DE cross section curve has a maximum of ${\text{3×10}}^{\text{−16}} {\mathrm{cm}}^{\mathrm{2}}$ near 15 eV. We have determined the branching fractions to the different dissociation limits and present atomic quantum yields for the DR process between 0 to 300 meV collision energy. The quantum yield of $\mathrm{O}{(}^1\mathrm{D)}$ is found to be $\text{1.17±0.05,}$ largely independent of the electron energy. Arguments are presented that the branching fraction to $\mathrm{O}{(}^3\mathrm{P)+}\mathrm{O}{(}^1\mathrm{S)}$ is negligible. The branching fraction to the $\mathrm{O}{(}^1\mathrm{S)+}\mathrm{O}{(}^1\mathrm{D)}$ is smaller than 0.06 and varies strongly as a function of collision energy. The $\mathrm{O}{(}^1\mathrm{S)}$ quantum yield is a strong function of electron temperature. Hence, the relative strength of the green, $\mathrm{O}{(}^1\mathrm{S),}$ and the red, $\mathrm{O}{(}^1\mathrm{D),}$ airglows may be used as a measure of the electron temperature of the upper atmosphere. A qualitative explanation is given of the consequences of nonadiabatic interactions in the dissociation step of the DR process.