MICROCANONICAL CORRELATION-ANALYSIS OF COLLISIONAL ENERGY-TRANSFER EFFICIENCIES IN UNIMOLECULAR REACTIONS

Available experimental data on the collisional energy transfer per col lision [Delta E] between the reactant molecules benzene, toluene, azul ene, and cycloheptatriene and various medium molecules are analyzed in terms of the concept of energy transfer efficiency beta(E). This quan tity is the ratio of the experimental land the statistical limit value for (Delta E) as obtained by the assumption of a microcanonical energ y redistribution. Although the statistical limit is typically more tha n 1 order of magnitude too high, it correlates very strongly with the experimental values with respect to the dependence on molecular comple xity, reactant energy, and medium temperature. We focus here on molecu lar complexity and show that the experimental data are very well repre sented by a simple geometrical correlation model wherein each of the t wo colliding molecules is represented by its own efficiency factor. Th e model may be used to extrapolate experimental data. It also gives ph ysical insight into the factors determining energy transfer efficiency and can be extended to incorporate more accurate statistical theories .