DEPENDENCE OF THE COLLISIONAL RELAXATION OF HIGHLY VIBRATIONALLY EXCITED POLYATOMIC-MOLECULES ON THE POPULATION-DISTRIBUTION FUNCTION

The influence of the population distribution function on the collisional relaxation of highly vibrationally excited polyatomic molecules is analyzed in a non-reactive system. Unimodal and bimodal energy distributions are considered. Calculations made with unimodal energy distributions showed that the energy decay is almost independent of its initial shape and also of the collisional transition probability models, provided they have the same dependence on energy. When the initial distribution is bimodal, the rate of energy decay, for constant average energy transferred, depends on the fraction of molecules excited, but if the decay is exponential, the energy loss profile is almost independent of the fraction q of molecules excited. These results are discussed in relation to the use of IR multiphoton absorption as an experimental technique for the study of energy transfer processes.