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 collision al relaxation of highly vibrationally excited polyatomic molecules is analyzed in a non-reactive system. Unimodal and bimodal energy distrib utions are considered. Calculations made with unimodal energy distribu tions showed that the energy decay is almost independent of its initia l shape and also of the collisional transition probability models, pro vided they have the same dependence on energy. When the initial distri bution is bimodal, the rate of energy decay, for constant average ener gy transferred, depends on the fraction of molecules excited, but if t he decay is exponential, the energy loss profile is almost independent of the fraction q of molecules excited. These results are discussed i n relation to the use of IR multiphoton absorption as an experimental technique for the study of energy transfer processes.