Mechanistic insight into the N2O + O(1D,3P) reaction: role of post-CCSD(T) corrections and non-adiabatic effects

Abstract

In the present work, we have studied the N₂O + O(¹D,³P) reaction using high level quantum chemical calculations along with non-adiabatic kinetics. For quantum chemical calculations, we used the post-CCSD(T) method, which includes corrections from full triple excitations and partial quadratic excitations at the coupled-cluster level. For both the paths (N₂ + O₂ and 2NO), we have computed the rate constants over a wide range of temperatures (100–500 K for singlet paths and 700–4000 K for triplet paths). To assess the accuracy of our computations, we have compared our results with various experimentally measured quantities (absolute rate constant, branching fraction, and crossover temperature) and found a good match with all of them. We recommend the Arrhenius expressions for singlet paths, which turn out to be 4.46 × 10⁻¹¹ exp(0.022/RT) cm³ molecule⁻¹ s⁻¹ and 7.12 × 10⁻¹¹ exp(0.024/RT) cm³ molecule⁻¹ s⁻¹ for N₂ + O₂ and NO paths, respectively. For triplet paths, our recommended Arrhenius expressions are 5.15 × 10⁻¹² exp(−15.35/RT) cm³ molecule⁻¹ s⁻¹ and 1.59 × 10⁻¹⁰ exp(−27.76/RT) cm³ molecule⁻¹ s⁻¹ for N₂ + O₂ and NO paths, respectively.