Vibronic interaction in transition metal complexes

When the vibrational and electronic motions are coupled, the intensity integral for the transition between jr (ground state) and - p (excited state) has the form 

An example will illustrate the above arguments. The ground state of a d1 octahedral complex ML6 is 2 Ag and the only excited state for this complex is 2Eg. In the Oh point group, Aj,z is Au- Also, this complex has the vibrational modes 

Therefore, for this electronic transition to have any intensity, it must be accompanied by a vibration of either Tiu or T2u symmetry. 

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