Quantitative parameters K and A calculated for the reaction path open a chance for new characterization of contacts between atoms in a system undergoing a reaction, by testing the stepwise evolution of their contributions to the vibrational energy along the way. Unlike the atomic and bond parameters describing inherent properties of a stationary system (e.g. CAA, CAB), the bond contributions to K and A report the energy required to make a step on the "optimal" path from reactants to products.