Franck-Condon principle framework

Fock-Dirac density matrix, 225-Framework, 379 Franck-Condon principle, 199 Free volume, 26, 27, 33... 

Nuclei move much more slowly than the much-lighter electrons, so when a transition occurs from one electronic state to another, it takes place so rapidly that the nuclei of the vibrating molecule can be assumed to be fixed during the transition. This is called the Franck-Condon principle, and a consequence of it is that an electronic transition is represented by a vertical arrow such as that shown in Figure 2.5 that is, an electronic transition occurs within a stationary nuclear framework. Thus the electronic transition accompanying the absorption of a photon is often referred to as a vertical transition or Franck-Condon transition. 

E. W. Schlag The intensities can in many cases be calculated from the Franck-Condon principle, but in some cases there are important exceptions that are most clearly interpreted in the inverse Bom-Oppenheimer (BO) framework. Here one clearly sees the superposition of Rydberg stacks from individual rotations or vibrations. 

The theoretical description of the kinetics of electron transfer reactions starts fi om the pioneering work of Marcus [1] in his work the convenient expression for the free energy of activation was defined. However, the pre-exponential factor in the expression for the reaction rate constant was left undetermined in the framework of that classical (activate-complex formalism) and macroscopic theory. The more sophisticated, semiclassical or quantum-mechanical, approaches [37-41] avoid this inadequacy. Typically, they are based on the Franck-Condon principle, i.e., assuming the separation of the electronic and nuclear motions. The Franck-Condon principle... 

The intensity derived from Afoi(so) will appear in the absorption spectrum distributed over the electronic origin and totally symmetric vibronic bands according to the Franck-Condon principle. This follows from the fact that a rigid molecular framework is assumed in the mixing... 

The mechanism of DIET was first discussed on the basis of the Franck-Condon principle. In this framework, the surface is electrically excited to a number of states, keeping the atomic location unchanged. In case of excitation to the repulsive part of the potential, ions or neutrals are released and desorbed when being accelerated by the repulsive potential as shown in Figure 8. This mechanism is called the Menzel-Gomer-Redhead mechanism. As for excitation by the impact of incident photons or electrons with... 

Electron-transfer reactions, which occur either by the inner-sphere or by the outer-sphere mechanism, are subject to restrictions defined by the Franck-Condon principle. The principle explains the distribution of relative intensities of the vibrational structure of an electronic transition. Namely, since the nuclei have a much larger mass than the electrons, electron transition takes place much faster than the nuclei can respond. Thus, the electron transition takes place in about 10" to 10 s, while the nuclei need about 10 s to respond (which is approximately the time of one vibration). This is the reason why electron density is rapidly built up in the new molecular region. The new electron density distribution acts upon the nuclei, which become subject to a new force field, causing them to vibrate. Since the nuclear framework remains unchanged with respect to its geometry during a very fast electronic transition, the expression vertical transition is used to describe this situation. 

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