Dynamics of Inelastic and Reactive Collisions of ¹⁶O(³P) with ¹⁵N¹⁸O

Abstract

The dynamics of O­(3P) + NO collisions were investigated at a collision energy of ⟨E coll⟩ = 84.0 kcal mol–1 with the use of a crossed molecular beams apparatus employing a rotatable mass spectrometer detector. This experiment was performed with beams of 16O atoms and isotopically labeled 15N18O molecules to enable the products of reactive and inelastic scattering to be distinguished. Three scattering pathways were observed: inelastic scattering (16O + 15N18O), O-atom exchange (18O + 15N16O), and O-atom abstraction (18O16O + 15N). All product channels exhibited a preponderance of forward scattering, but scattering over a broad angular range was also observed for all products. For inelastic scattering, an average of 90% of the collision energy is retained in the translation of 16O and 15N18O. On the other hand, for O-atom exchange (which also leads to O + NO products), the collision energy is partitioned roughly evenly between the translation of 18O + 15N16O and the internal excitation of 15N16O. The available energy for O-atom abstraction is significantly lower than the collision energy because of the endoergicity of this reaction, but the available energy is again roughly evenly partitioned between the translation of 18O16O + 15N and the internal excitation of the molecular (O2) product. The relative yields of the three scattering pathways were determined to be 0.751 for inelastic scattering, 0.220 for O-atom exchange, and 0.029 for O-atom abstraction.

Reactive and Nonreactive Collisions between NO(X2Π) and O(3P) under Hyperthermal Conditions

“…Our QCT calculations of high-energy NO + O collisions, which assume electronic adiabaticity, qualitatively reproduce the experimental translational energy distributions . The angular distributions of the inelastic and exchange channels are found to be dominated by the forward scattering, also consistent with experiment .…”

“…These thresholds are indicated in Figure . The reasonably good agreement with experimental translational energy distributions seems to suggest that these higher channels do not play a significant role, but they cannot be ruled out completely.…”

“…Figure displays the comparison of the weighted average DCSs of the three channels with the measured angular distributions with the experimental uncertainties provided as the shaded areas . Because the experiment did not measure the absolute value of cross-sections, these comparisons are made by normalizing the area below the angular distributions.…”

“…As mentioned earlier, the abstraction DCS is dominated by contributions from the quartet state, which not only has a larger weight but also is more reactive. We note in passing that the experimental instrument can only detect a range of scattering angles in the lab frame, and the DCSs are obtained by assuming that the separability of the translational and angular distributions …”

“…The present work is motivated by the recent crossed molecular beam study of the hyperthermal 15 N 18 O­(X 2 Π) + 16 O­( 3 P) collision by Minton and co-workers . At a collision energy of 84 kcal/mol, they observed three channels, namely, the abstraction, exchange, and inelastic scattering.…”