Kinetics of associative detachment of O - + N 2 and dissociative attachment of e - + N 2 O up to 1300 K: chemistry relevant to modeling of transient luminous events.

The rate constants of O - + N 2 → N 2 O + e - from 800 K to 1200 K and the reverse process e - + N 2 O → O - + N 2 from 700 K to 1300 K are measured using a flowing afterglow - Langmuir probe apparatus. The rate constants for O - + N 2 are well described by 3 × 10 -12 e -0.28 eV kT -1 cm 3 s -1 . The rate constants for e - + N 2 O are somewhat larger than previously reported and are well described by 7 × 10 -7 e -0.48 eV kT -1 cm 3 s -1 . The resulting equilibrium constants differ from those calculated using the fundamental thermodynamics by factors of 2-3, likely due to significantly non-thermal product distributions in one or both reactions. The potential surfaces of N 2 O and N 2 O - are calculated at the CCSD(T) level. The minimum energy crossing point is identified 0.53 eV above the N 2 O minimum, similar to the activation energy for the electron attachment to N 2 O. A barrier between N 2 O - and O - + N 2 is also identified with a transition state at a similar energy of 0.52 eV. The activation energy of O - + N 2 is similar to one vibrational quantum of N 2 . The calculated potential surface supports the notion that vibrational excitation will enhance reaction above the same energy in translation, and vibrational-state specific rate constants are derived from the data. The O - + N 2 rate constants are much smaller than literature values measured in a drift tube apparatus, supporting the contention that those values were overestimated due to the presence of vibrationally excited N 2 . The result impacts the modeling of transient luminous events in the mesosphere.