Quasiclassical trajectory study of NO vibrational relaxation by collisions with atomic oxygen

Abstract

Room-temperature and temperature-dependent thermal rate constants are calculated for the state-to-state vibrational relaxation of NO(v ⩽ 9) by atomic oxygen using the quasiclassical trajectory method and limited ab initio information on the two lowest O + NO potential-energy surfaces which are responsible for efficient vibrational relaxation. Comparisons of the theoretical results with the available experimental measurements indicate reasonable agreement for the deactivation of NO(v = 2, 3) at 300 K and NO(v = 1) at 2700 K, although the calculated relaxation rate constant for NO(v = 1) at 300 K is approximately a factor of two below the measured value. The state-to-state relaxation rate coefficients involve the formation of long-lived collision complexes and indicate the importance of multiquantum vibrational relaxation consistent with statistical behaviour in O + NO collisions. The present results, combined with recent measurements of vibrational relaxation for NO(v = 2, 3), suggest that the current atmospheric models of NO cooling rates require higher atmospheric temperatures and/or an increase in the NO/O number densities.