Time resolved laser induced infrared fluorescence studies have been performed to obtain the rate constants of energy transfer of CO2(ngr;3) in mixtures with C2H2, C2H4, and C2H6at temperatures between 220 and 300 K. A pulsed 10.6 mgr;m CO2laser light has been used to directly excite the CO2molecules at low temperatures. The CO2selfhyphen;relaxation was measured and the results are in agreement with previous measurements. The rate constants for the transfer of energy in the CO2ndash;C2H2system show normal temperature behavior, (rate constant increases as the temperature increases) associated with large energy defect and caused by shorthyphen;range repulsive forces. The rate constants for the systems CO2ndash;C2H4and CO2ndash;C2H6show an inverse temperature effect, (rate constant increases as the temperature decreases) associated with near resonant energy exchange and longhyphen;range attractive forces between the molecules. The observed behavior with temperature for the three systems is explained using a Morse potential which includes repulsive and attractive terms to describe the interaction between the molecules and a probability expression formulated by H. K. Shin, to calculate the energy transfer probabilities of some important reactions considered for each system.
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