Unimolecular reaction dynamics of persistent collision complexes

The unimolecular decomposition of chemically activated (OCH4)dagger complexes, O(D-1(2)) + CH4 --> (OCH4)dagger --> OH(X; upsilon < 4, N) + CH3 has been probed via polarised, Doppler-resolved laser-induced fluorescence spectroscopy of the scattered OH(X; upsilon, N). The product state-resolved differential cross-sections and pair-correlated translational energy distributions are discussed in the light of: (i) a real-time study of the reaction by van Zee and Stephenson, (ii) earlier measurements of the product-state distributions in OH and CH3 and (iii) the results of pair-correlated phase-space-theory calculations. In particular, the relationship between 'lifetimes' and 'clock rates' is explored to provide an overall rationale for the experimental observations on the basis of restricted vibrational redistribution (adiabaticity) within the collision complex and the retention of some memory of its initial preparation, revealed through product-state specific opacity functions.