A trajectory surface-hopping study of mode specificity in the predissociation of N2O

A classical trajectory surface-hopping study of the effects of initial mode excitation on the spin-forbidden predissociation in a model of N2O reveals mode specificity. Incomplete energy randomization together with significant variation in energies of the surface crossing points with molecular geometry lead to changes in the accessibility of the dissociation channel and hence the rate of reaction when different modes are excited. The variations in the predissociation rate are most marked at relatively low energies. At higher energies, although energy randomization is still incomplete, there is less dispersion in the rate constants. This is attributed to the fact that at high energies a larger percentage of the crossing points become accessible and thus the directionality of the initial motion is less relevant to the rate.