Rate constant determination of the reaction of metastable N(²D,²P) with NO₂ using moderated nuclear recoil atoms

The kinetics of the reaction N(²D,²P) + NO₂ were studied by using moderated nuclear recoil atoms to generate thermalized metastable atomic nitrogen, ²D and ²P, at a [NO₂]/[N] ratio of 10¹³. Branching ratios were obtained for the following channels of reaction: N + NO₂ → N₂O + O (k_1a); N + NO₂ → 2NO (k_1b); N + NO₂ → N₂ + O₂ (k_1c); N + NO₂ → N₂ + 2O (k_1d). The distribution of channels 1a:1b:(1c + 1d) was measured to be 1.00:0.65:0.27. An upper limit for the overall rate constant for reaction was also evaluated at 3.3 × 10^-13 cm³ molecule^-1 s^-1 (293 K) by using competitive kinetic measurements of the formation of radioactive nitrogen-13 labeled products. This rate constant is at least an order of magnitude smaller than previously reported values for the ground-state N(⁴S) + NO₂ reaction.