On the theory of the reaction rate of vibrationally excited CO molecules with OH radicals

The dependence of the rate of the reaction CO+OH -> H+CO2 on the CO-vibrational excitation is treated here theoretically. Both the Rice-Ramsperger-Kassel-Marcus (RRKM) rate constant k(RRKM) and a nonstatistical modification k(non) [W.-C. Chen and R. A. Marcus, J. Chem. Phys. 123, 094307 (2005).] are used in the analysis. The experimentally measured rate constant shows an apparent (large error bars) decrease with increasing CO-vibrational temperature T-v over the range of T-v's studied, 298-1800 K. Both k(RRKM)(T-v) and k(non)(T-v) show the same trend over the T-v-range studied, but the k(non)(T-v) vs T-v plot shows a larger effect. The various trends can be understood in simple terms. The calculated rate constant k(v) decreases with increasing CO vibrational quantum number v, on going from v=0 to v=1, by factors of 1.5 and 3 in the RRKM and nonstatistical calculations, respectively. It then increases when v is increased further. These results can be regarded as a prediction when v state-selected rate constants become available.