Mechanistic insight into the N 2 O + O( 1 D, 3 P) reaction: role of post-CCSD(T) corrections and non-adiabatic effects.

In the present work, we have studied the N 2 O + O( 1 D, 3 P) 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 (N 2 + O 2 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 ) cm 3 molecule -1 s -1 and 7.12 × 10 -11  exp(0.024/ RT ) cm 3 molecule -1 s -1 for N 2 + O 2 and NO paths, respectively. For triplet paths, our recommended Arrhenius expressions are 5.15 × 10 -12  exp(-15.35/ RT ) cm 3 molecule -1 s -1 and 1.59 × 10 -10  exp(-27.76/ RT ) cm 3 molecule -1 s -1 for N 2 + O 2 and NO paths, respectively.