Energy partitioning in the reaction 16O(1D)+H2 18O→16OH+18OH. II. The distribution of 16OH and 18OH

Abstract

The reaction of O(1D) with water proceeding to two OH molecules has been studied by isotopic labeling of the oxygen atom in the water molecule in order to distinguish between the two chemically identical product molecules and to determine the product state distribution. A large fraction (∼0.6) of the available energy is released as translation. The vibrational energy is preferentially channeled into the new (16OH) bond, and the 16OH vibrational distribution is ’’hotter’’ than that expected on prior (microcanonical) grounds. The opposite is true for the 18OH (old bond), which is produced almost exclusively (≳0.9) in the ground vibrational state. The rotational energy is, however, equipartitioned among the two bonds. For each vibrational manifold, the rotational distribution is well characterized by a linear surprisal. Using a reduced variable, the rotational surprisal parameter is found to be independent of the vibrational state. Due to the high fraction of available energy released as translation, the fraction of energy in the rotation (∼0.2) is less than expected on prior grounds and the surprisal parameter is positive. The ratio of the rotational surprisal parameters determined for 16OH and 18OH by surprisal analysis is in close agreement with that predicted by the equipartitioning of the rotational energy between the two OH molecules. The OH was found to be statistically distributed between its two possible spin states.