Question

When we justify the presence of electronic transitions forbidden by Laporte selection rule, the coupling between electronic and vibrational states help us. Why we say that in this way we are overcoming the Born-Oppenheimer approximation? Possibly I'm searching for an intuitive explanation and/or a theoretical one.

Answer 1

The coupling between electronic and vibrational states helps to justify the presence of electronic transitions forbidden by the Laporte selection rule and overcome the Born-Oppenheimer approximation in molecular quantum mechanics.

Step-by-step explanation:

The Born-Oppenheimer approximation is a widely used approximation in molecular quantum mechanics that separates the electronic and nuclear motion in a molecule. It assumes that the electronic and nuclear wavefunctions can be treated independently. However, this approximation breaks down when electronic transitions forbidden by the Laporte selection rule occur. In these cases, the coupling between electronic and vibrational states helps to justify the presence of these forbidden transitions and overcome the Born-Oppenheimer approximation.