What is going on in the chemists flask

Let us imagine the molecular ttynamics on eneigy hypersurface calculated using a quantum-mechanical method (classical force fields are not appropriate since they offer non-breakable chemical bonds). The tystem is represented by a point that slides downhill (with an increasing velocity) and climbs uphill (with deceasing velocity). The system has a certain kinetic energy, because chemists often heat their flaslffi. 

Let us assume that, first the tystem wanders through those regions of the hypersurface which are far from other electronic states in the energy scale. In such a situation, the adiabatic approximation (Chapter 6) is justified and the electronic 

Intermolecular Motion of Electrons and Nuclei Chemical Reactions 

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