QUASI-CLASSICAL TRAJECTORY STUDY OF NO VIBRATIONAL-RELAXATION BY COLLISIONS WITH ATOMIC OXYGEN

Room-temperature and temperature-dependent thermal rate constants are calculated for the state-to-state vibrational relaxation of NO(v less than or equal to 9) by atomic oxygen using the quasiclassical trajecto ry method and limited ab initio information on the two lowest O + NO p otential-energy surfaces which are responsible for efficient vibration al relaxation. Comparisons of the theoretical results with the availab le experimental measurements indicate reasonable agreement for the dea ctivation of NO(v = 2, 3) at 300 K and NO(v = 1) at 2700 K, although t he calculated relaxation rate constant for NO(v = 1) at 300 K is appro ximately a factor of two below the measured value. The state-to-state relaxation rate coefficients involve the formation of long-lived colli sion 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 vibrationa l relaxation for NO(v = 2, 3), suggest that the current atmospheric mo dels of NO cooling rates require higher atmospheric temperatures and/o r an increase in the NO/O number densities.