Simulation of O2-N Collisions on ab-initio Potential Energy Surfaces

Abstract

Investigation of O2-N collisions is performed by means of the Quasi-Classical Trajectory method on the two lowest ab-initio potential energy surfaces. A complete set of boundbound and bound-free transition rates is obtained for each precollisional rovibrational state. Special attention is paid to the vibrational and rotational relaxation of oxygen as a result of chemically non-reactive interaction with nitrogen atoms. It is found that the vibrational relaxation of oxygen occurs via the formation of an intermediate NO2 complex with a large number of mutual internuclear vibrations before the final departure of the projectiles. The efficient energy randomization results in rapid vibrational relaxation at low temperatures, compared to other molecular systems with a purely repulsive potential. The vibrational relaxation time, computed by means of master equation studies, is nearly an order of magnitude lower than the relaxation time in N2-O collisions. The rotational nonequilibrium starts to play a significant effect at translational temperatures above 8000 K. The present work provides convenient relations for the vibrational and rotational relaxation times as well as for the quasi-steady dissociation rate coefficient and thus fills the gap in data due to a lack of experimental measurements for this system.

Nitric Oxide Production by Centimeter-Sized Meteoroids and the Role of Linear and Nonlinear Processes in the Shock Bound Flow Fields

“…The production of NO in hypersonic flows is closely correlated to the degree of dissociation of N 2 and O 2 , in addition to thermal history in different regions of the flow field. Nitric oxide formation in shock forming hypersonic flows has been intensively investigated in recent years (e.g., [43][44][45][46][47]). In rarefied air, O 2 generally dissociates in the range of 2000 to 4000 K [11,41].…”

Application of the 3D Forced Harmonic Oscillator Model in the DSMC Method

“…The FHO-FR mechanism does not take into account strong attractive forces that dominate such collisions, and it does not include highly possible exchange reactions, which have shown to significantly decrease the VT relaxation time [11]. As a result, it may not reproduce the unconventional temperature dependence of τ v increasing with the gas temperature at high T, which was established recently for O 2 -N collisions [44]. Similar to the one-dimensional (1-D) FHO, discussed in [12], the FHO-FR provides VT rates for N 2 -N collisions that are in good agreement with QCT rates for single-quantum VT jumps (not shown here) but significantly differ from them for multiquantum jumps.…”