Electronic to vibrational energy transfer

1. Mar 16, 2012

Katastrofa

Let's say I have some simple molecule excited to higher electronic level. Is it possible that it goes back to its ground state by transferring the excitation energy into its vibrational degrees of freedom? I believe it is... what are the selection rules for such a process?
TIA

2. Mar 17, 2012

DrDu

Yes, that's called a vibronic transition. Usually there are many vibrational modes involved: There is one mode which has the right symmetry so as to couple the ground and the excited states, so if the grounnd state is totally symmetric, the symmetry label of that mode times the symmetry of the excited electronic state has to contain A1g. Usually that mode changes by only one quantum. Then there are many totally symmetric modes which change equilibrium position in the transition and lead to the so called Franck Condon factors.

Edit: The non-symmetric modes that make the coupling are called promoting modes.

Last edited: Mar 17, 2012