Kinetics of the reaction between atomic nitrogen and molecular oxygen in the ground ( 3 ∑ - g ) and first excited ( 1 ∆ g ) states

Abstract

Rate constants for the reaction N + O 2 ( 1 ∆ g ) → k 1 NO + O (1) have been measured at four temperatures, and fitted to an Arrhenius expression, k 1 = A exp ( ─ E a / RT ). The results indicate that A ≤ 2 x 10 -14 molecule -1 cm 3 s -1 and < 1.2 kcal (5.0 kJ ) mol -1 : at room temperature (300 K ), k 1 = 2.7 ± 1.0 x 10 -15 molecule -1 cm 3 s -1 . Reaction (1) cannot, therefore, proceed fast enough at 200 K for it to be an important source of nitric oxide in the atmospheric D-region. The rate constant for the reaction N + O 2 ( 3 ∑ ─ g ) → k 2 NO + O (2) has been measured at 302 K to be 1.08 ± 0.10 x 10 -16 molecule -1 cm 3 s -1 . This value, taken together with the data of earlier workers, suggests that k 2 = 1.5 x 10 -11 exp (—7.1/ RT ) molecule -1 cm 2 s -1 . A possible explanation for the difference in pre-exponential factors for reactions (1) and (2) is presented.