(adsbygoogle = window.adsbygoogle || []).push({}); Theory and my Understanding:

So I understand how the frank condon principle lets us effect electronic transitions instantaneously, since the motion of nuclei (on the timescale of such electronic transitions) is quite slow.

Consequently, when a photon of light is absorbed you can have an electron being promoted from the S^{x}_{0}to the S^{y}_{1}where S represents the singlet state and x and y are vibrational levels (x>y)

My Question

What effects how much the upper curve is translated over to the right-hand-side, with respect, to the lower curve ?

My Interpretation

When an electron is promoted from S^{0}_{0}to S^{2}_{1}, for example, the electron is being put into an anti-bonding orbital consequently weakening bonds and leading to a greater vibrations.

The more anti-bonding character the S_{1}state has the greater the amount by which the upper curve is translated over to the right-hand-side and hence the larger the vibrations.

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# Frank-Condon Principle - Potential Energy Surfaces

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