Schlag, E. W.; Neusser, H. J.; Riedle, Eberhard
High Resolution Sub-Doppler Experiments on Benzene.
In: AIP conference proceedings / American Institute of Physics, Vol. 172: S. 628-633
It is shown that sub-Doppler spectroscopy enables one to resolve
individual rotational states in the S^ manifold of polyatomic molecules.
This i s an essential to the understanding of the primary
photophysics within the molecule. Spectra of benzene are found to undergo
substantial changes as the vibrational energy i s raised within S^.
Due to the increased density of vibrational states, Coriolis coupling,
which is already seen at low energies, can lead to effective IVR above
3000 cm""1 excess energy. This onset of IVR may be responsible for the
onset of "Channel Three" in benzene and probably produces gross changes
in the photophysical behavior of any polyatomic molecule.