1. Vibrational spectra of complex molecules
Lecture 6
Vibrational spectra of complex molecules

2. R-Q-P

4. Gas
Solid matrix
Sharp peaks!

5. Liquid acetone
Acetone in a
solid matrix
(*- admixtures)
Sharp peaks!

6. Fermi Resonance Overtone: weak (forbiden) Resonance line:
much stronger, shifted,
and allowed
Two conditions must be satisfied for the occurrence of Fermi Resonance:
(1) the two vibrational states of a molecule transform according to the same irreducible representation of the molecular point group.
(2) The energies of the transitions (accidentally) have almost the same energy.

7. Overtone
Fundamental band
Fermi Resonance