Global Control of Suprathreshold Reactivity by Quantized Transition States

We present evidence that the accurate quantum mechanical probability of the reaction of H with H₂ is globally controlled by quantized transition states up to very high energies. The quantized transition states produce steplike features in the cumulative reaction probability curves that are analyzed up to energies of 1.6 eV; the analysis clearly associates these steps (or “thresholds”) with quantized dynamical bottlenecks that control the passage of reactive flux to products. We have assigned bend and stretch quantum numbers to the modes orthogonal to the reaction coordinate for all these transition states on the basis of threshold energies of semiclassical vibrationally adiabatic potential energy curves and vibrationally specific cumulative reaction probability densities.