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.