Dissociative recombination and excitation of O-2(+): 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 O-2(+) in its electronic and vibrational g round state using a heavy ion storage ring. The absolute DR cross section h as been determined over an electron collision energy range from 1 meV to 3 eV. The thermal DR rate coefficient is derived; alpha (T-e)=2.4x10(-7)(300/ T-e)(0.70 +/-0.01) cm(3) s(-1), for T > 200 K. The threshold for DE was obs erved near its energetic threshold of 6.7 eV. The DE cross section curve ha s a maximum of 3x10(-16) cm(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 quantu m yield of O(D-1) is found to be 1.17 +/-0.05, largely independent of the e lectron energy. Arguments are presented that the branching fraction to O(P- 3)+O(S-1) is negligible. The branching fraction to the O(S-1)+O(D-1) is sma ller than 0.06 and varies strongly as a function of collision energy. The O (S-1) quantum yield is a strong function of electron temperature. Hence, th e relative strength of the green, O(S-1), and the red, O(D-1), 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 inte ractions in the dissociation step of the DR process. (C) 2001 American Inst itute of Physics.