The Franck-Condon principle: considerations on the correctness of its formulation

This paper is intended to show that the Franck-Condon principle is erroneously formulated when expressed in terms of vertical electronic transitions which take place very rapidly in comparison with the period of molecular vibration. The fallacy lies in presupposing the possibility of a measurement that violates the Heisenberg uncertainty principle. It is suggested that is that the correct enunciate is as follows: the square of the overlap integral of vibrational wave functions determines the relative intensity of the vibrational bands within an electronic spectrum