Temperature-jump and trajectory studies of the quenching of CO2(010) by atomic oxygen

Abstract

A new variant of the temperature-jump method has been used to measure the rate of quenching of CO₂(010) by O(³P). The value found for the rate constant at room temperature is 1.2 ± 0.2 × 10^–12 cm³ molecule^–1 s^–1, in good agreement with a previous laboratory study. Our trajectory calculations show that such a large value of the room-temperature rate constant is not explicable in terms of an impulsive (Landau–Teller) mechanism but can be understood in terms of a curve-crossing (Nikitin) mechanism. However, the impulsive mechanism is still required to account for the strong temperature dependence of previous high-temperature, shock-tube results. Preliminary measurements of the rate of quenching of N₂O(010) by O(³P) give a rate constant value similar to that found for CO₂, which implies that formation of a bound triplet state of CO₃ plays very little part in the quenching process for CO₂(010).