Origin of the giant circular dichroism of vibronic f–f transitions

Taking into account the space inhomogeneity of the light electromagnetic wave, a new quantum mechanical expression for the natural optical activity (NOA) of electron transitions has been obtained, which is consistent with the phenomenological theory. It is shown that properties of the NOA of parity forbidden f–f transitions substantially differ from those of allowed transitions. The experimentally observed large NOA of the f–f transitions and extremely large (close to unity) NOA of vibrational repetitions of the f–f transitions are qualitatively explained on the basis of the obtained theoretical expression.