## MODEL STUDIES OF MODE-SPECIFICITY IN UNIMOLECULAR REACTION DYNAMICS

Essentially exact quantum mechanical calculations are carried out to determine the energies and lifetimes of the quasi-bound states for a system of two (non~linearly) coupled oscillators (one of which is harmonic, the other being able to dissociate). For weak coupling the system displays mode-specificity, i.e., the unimolecular rate constants are not a monotonic function of the total energy, but increased coupling and frequency degeneracy tends to destroy mode-specificity. A somewhat surprising result is that for a given coupling the degree of modespecificity is roughly independent of the energy, in marked contrast to the fact that there is an energetic thresholdmore »