reflects the role of individual atom in a particular, physically realistic vibration pattern affecting the electronic energy. This opens a novel observation point potentially valuable for a chemical reaction: observation of the variable role of displacement of individual atoms in disturbing the electronic energy of a whole system. The atomic eigenvalues have still the meaning of force constants, hence a collection of eigenvalues and eigenvectors calculated on a IRC reaction trajectory provide comprehensive information on an evolution of bonding interactions in a system and on the role of individual atoms therein.