Vibrationally Induced Perturbations in Molecular Electron Distributions

It is demonstrated that second-order perturbation theory is useful in determining the manner in which the electron density present in a molecule is changed during a nuclear vibration. Furthermore, it is shown that one nuclear motion will lead to a particularly favorable electronic distortion such that this motion is energetically favored over the other possible motions of the molecule. This allows one to employ the theory to predict the symmetry of the reaction coordinate in both unimolecular and bimolecular reactions. The chemical implications of the electron density changes are discussed.