  Proton transfer rates and mechanisms are studied in mesoscopic, liquid-state,
molecular clusters. The proton transfer occurs in a proton-ion complex solvated
by polar molecules comprising the cluster environment. The rates and mechanisms
of the reaction are studied using both adiabatic and non-adiabatic molecular
dynamics. For large molecular clusters, the proton-ion complex resides
primarily on the surface of the cluster or one layer of solvent molecules
inside the surface. The proton transfer occurs as the complex undergoes
orientational fluctuations on the cluster surface or penetrates one solvent
layer into the cluster leading to solvent configurations that favor the
transfer. For smaller clusters the complex resides mostly on the surface of the
cluster and proton transfer is observed only when the complex penetrates the
cluster and solvent configurations that favor the proton transfer are achieved.
Quantitative information on the cluster reaction rate constants is also
presented.
