Crude Born-Oppenheimer approximation

Force constants, crude Born-Oppenheimer approximation, hydrogen molecule, minimum basis set calculation, 545-550 Forward peak scattering, electron nuclear... 

Integral properties, crude Born-Oppenheimer approximation ... 

In the crude Born-Oppenheimer approximations, the oscillator strength of the 0-n vibronic transition is proportional to (FJ)2. Furthermore, the Franck-Condon factor is analytically calculated in the harmonic approximation. From the hamiltonian (2.15), it is clear that the exciton coupling to the field of vibrations finds its origin in the fact that we use the same vibration operators in the ground and the excited electronic states. By a new definition of the operators, it becomes possible to eliminate the terms B B(b + b ), BfB(b + hf)2. For that, we apply to the operators the following canonical transformation ... 

Vibrational sideline structure retains the polarization of the purely electronic excitation. Within the crude Born-Oppenheimer approximation, only totally symmetric vibrational modes are coupled to an electronic transition. Consequently, all vibrational sidelines have the same polarization as the purely electronic component (electronic origin or zero phonon line). There are two circumstances... 

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