Intramolecular vibrational redistribution dissipative

This chapter is concerned with how energy deposited into a specific vibrational mode of a solute is dissipated into other modes of the solute-solvent system, and particularly with how to calculate the rates of such processes. For a polyatomic solute in a polyatomic solvent, there are many pathways for vibrational energy relaxation (VER), including intramolecular vibrational redistribution (IVR), where the energy flows solely into other vibrational modes of the solute, and those involving solvent-assisted processes, where the energy flows into vibrational, rotational, and/or translational modes of both the solute and the solvent. 

These emission spectra in helium droplets revealed the dissipation of vibrational excitation energy prior to radiative decay. However, the particular mechanism for the dissipation, whether it proceeds directly into the helium environment or whether intramolecular vibrational redistribution (IVR) is preceding the dissipation, is not revealed by the data. In the case of phthalocyanine the gas phase emission spectra of excited vibronic levels indicate a radiative rate constant which exceeds that of IVR. Under the assumption that also in helium droplets IVR has a smaller rate constant than the radiative decay, the decay rate of vibronic levels as measured in... 

---