Measurements of the relative rate constants for the quenching of O(1D) atoms by N2O and N2 and the branching ratio of the N2O reaction at 23 and −96 °C

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

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.

Kinetics of O2(aΔg) and I(2P1/2) in the Photochemistry of N2O/I2 Mixtures

The recent demonstration of a discharge-driven oxygen-iodine laser has generated renewed interest in the kinetics of iodine interacting with electronically excited O2 and atomic O. Kinetic measurements that are of relevance to the laser have been carried out using 193 nm pulsed laser photolysis of N2O/I2/CO2 mixtures. Singlet oxygen was generated in this system by the reaction O(1D)+N2O-->O2(a1Deltag, X3Sigma-g)+N2. The fraction of electronically excited O2 produced by this channel was shown to be >0.9. The secondary photochemistry of the N2O/I2/CO2 system was characterized by monitoring the time histories of I(2P1/2), I2, IO, and O2(a). Kinetic modeling of these data was used to determine the rate constant for the deactivation of I(2P1/2) by O(3P) (k=(1.2+/-0.1)x10(-11) cm3 s(-1)). Quenching of I(2P1/2) by O(3P) is suppressed in the discharge-driven laser by using NO2 to scavenge the O atoms. The reaction O(3P)+NO2-->O2+NO is sufficiently exothermic for the production of O2(a), and it has been speculated that this channel may be significant in the laser excitation kinetics. Photolysis of NO2 was used to probe this reaction. O2(a) was not detected, and an upper bound of <0.1 for its production in the reaction of O(3P) or O(1D) with NO2 was established.

Nonadiabatic energy transfer studies of O(1D)+N2(X 1Σg+)→O(3P)+N2(X 1Σg+) by time-dependent wave packet

Three-dimensional time-dependent quantum calculations have been performed on two/three coupled potential surfaces, including the singlet surface 1 (1)A(') and two triplet surfaces 1 (3)A(') and 1 (3)A("), for the electronic quenching process of O((1)D)+N(2)(X (1)Sigma(g) (+))-->O((3)P)+N(2)(X (1)Sigma(g) (+)). An extended split-operator scheme was employed to study this nonadiabatic process. Two types of singlet surface 1 (1)A('), namely, double many body expansion (DMBE2) were used in the calculations, along with spin-orbit couplings of Nakamura-Kato and with a constant value of 80 cm(-1). All the calculated probabilities are resonance dominated, with a general decreasing trend within the investigated collision energy range. The probability involving three potential energy surfaces is approximately two times as high as that on two potential energy surfaces. At low collision energies, the calculations on the ZPM2 surface produced much larger probability than that on the DMBE2 surface, but the difference was diminishing as the collision energy became high. The behavior of the probability on DMBE2/ZPM2 surfaces at low energies indicates that the ZPM2 surface dominates over the DMBE2 surface in the description of the process. However, the DMBE2 surface has been modified by removing the unreasonable barrier. The estimated quenching cross sections both on the ZPM2 surface and on the modified DMBE2 surface in the three-coupled-surface calculations agree with the experimental measurement. Also, a rather insensitive characteristic of the probability relative to the analytical function form of spin-orbit coupling is revealed.