Dynamics of the reaction of oxygen atoms with carbon suboxide

The dynamics of the O(³P)+C₃O₂→3CO reaction (ΔH°=-115 kcal/mole) has been investigated by means of a CO laser resonance absorption technique. The reaction mixtures consisted of NO ₂ and C₃O₂, with He or SF₆ dilution. The O(³P) atom was generated by the flash photolysis of the NO ₂ above 300 nm. The three CO's formed in the reaction were found to carry vibrationally about 19% of the total available energy, with an apparent near statistical population distribution. The results of an ¹⁸O- labeled experiment, however, indicate that the two CO's originating from the parent C₃O₂ molecule are vibrationally much colder (〈E_v〉≃ 4.2 kcal/mole) than that from the reaction of the O atom with the center C atom (〈E_v〉≃15 kcal/mole). This result is attributed to the incomplete randomization of the reaction energy in the dissociating C₃O₃ complex. Possible reaction mechanisms are presented.