Absolute rate constant and O(³P) yield for the O(¹D)+N₂O reaction in the temperature range 227 K to 719 K

S. Vranckx (1) , J. Peeters (1) , S. A. Carl (1)

1 Department of Chemistry [Leuven]

We have determined, in the temperature range 227 K to 719 K, the absolute rate constant for the reaction O(¹D)+N₂O ? products and, in the temperature range 248 K to 600 K, the fraction of the reaction that yields O(³P). Both the rate constants and product yields were determined using a recently-developed chemiluminescence technique for monitoring O(¹D) that allows for higher precision determinations for both rate constants, and, particularly, O(³P) yields, than do other methods. We found the rate constant, k_R1, to be essentially independent of temperature between 400 K and 227 K, having a value of (1.37±0.09)×10^?10 cm³ s^?1. For temperatures greater than 450 K a marked decrease in value was observed, with a rate constant of only (0.94±0.11)×10^?10 cm³ s^?1 at 719 K. The rate constants determined over the 227 K?400 K range show very low scatter and are significantly greater, by 20% at room temperature and by 15% at 227 K, than the current recommended values. The fraction of O(³P) produced in this reaction was determined to be 0.002±0.002 at 250 K rising steadily to 0.010±0.004 at 600 K, thus the channel producing O(³P) can be entirely neglected in atmospheric kinetic modeling calculations. A further result of this study is an expression of the relative quantum yields as a function of temperature for the chemiluminescence reactions (k_CL1) C₂H+O(¹D) ? CH(A)+CO and (k_CL2) C₂H+O(³P) ? CH(A)+CO, both followed by CH(A) ? CH(X)+h?, as k_CL1(T)/k_CL2(T)=(32.8T?3050)/(6.29T+398).

Domaines: Océan, Atmosphère

S. Vranckx, J. Peeters, S. A. Carl. Absolute rate constant and O(³P) yield for the O(¹D)+N₂O reaction in the temperature range 227 K to 719 K. Atmospheric Chemistry and Physics Discussions, 2008, 8 (3), pp.8881-8912. ⟨hal-00304163⟩