Vibrational-energy redistribution in highly excited molecules

This paper presents the author's overall view of the high-energy vibrational-state manifold of the polyatomic molecule as that of a ''network'' of extreme motion (EM) bands embedded in an optically inactive quasi-continuum of evenly-mixed states. The bands are organized in vertical columns corresponding to the high-frequency modes. Usually these are all the stretching vibrations; bands within the same column are optically (IR or Raman) active. That is, transitions between consecutive bands are strong whereas overtone-like transitions are weaker. The ground state is common to all the pure EM progressions. In addition, there are other progressions that begin with some combination band. A band in a progression may be isolated and describe an extreme motion in the relevant mode. It may also be (due to anharmonic resonances) joint with other progressions. These joint bands are the horizontal connections in the network. They are responsible for vibrational-energy redistribution monitored by optical means