Activated chemical reactions driven by accepted fluctuations

A unified point of view for activated chemical reactions in gas and condensed phases is discussed. Contact is made with mechanical and dynamical formulations (e.g., simulations based on classical trajectories ) as well as with statistical theories of reaction rates and their thermodynamic formulations. This approach is consistent with existing theories but also covers additional physico-chemical situations which we suggest are common. Three examples are reviewed: activated atom exchange in solution, activated desorption from a surface and dissociation of clusters, which demonstrate that dynamical manifestations such as selective energy requirements can be observed in many-body systems.