Statistical-diabatic model for state-selected reaction rates. Theory and application of vibrational-mode correlation analysis to OH(n_OH) +H₂(n_HH)→H₂O+H

The state-selected reaction rates OH(n_OH = 0,1) + H ₂(n_HH = 0,1)→H₂O + H are calculated by an extension of variational transiton state theory. The reactant vibrational modes are assumed to correlate diabatically with generalized normal modes of a generalized activated complex. Using the Walch-Dunning-Schatz-Elgersma ab initio potential energy surface, the theory predicts that excitation of H₂ is 19-68 times more effective than excitation of OH in promoting reaction at 300 K, where the range of values corresponds to different possible assumptions about the quantal effects on reaction-coordinate motion. These values are in much better agreement with the experimental value (about 100) than is a calculation based on the conventional transition state, which yields 2 × 10⁴.