Laser induced vibrational fluorescence decay measurements have been made for thelpar;v7plus;v8rpar;andlpar;v6plus;v10rpar;combination bands of C2H4gas. The rate of vibrationhyphen;translationsol;rotation energy transfer in ethylene was found to be7.23plusmn; 0.3thinsp;msecminus;1middot;torrminus;1. This result is in agreement with one sound absorption study but disagrees with several ultrasonic dispersion studies. The rate constants for deactivation of C2H4during collisions with CH4and C2H6were also determined as8.0thinsp;msecminus;1middot;torrminus;1and92.0thinsp;msecminus;1middot;torrminus;1, respectively. The efficiency of ethane as a collision partner is almost certainly an indication of near resonant vibrational energy transfer between the C2H4and C2H6molecules. The dependence of the 5hyphen;mgr; and 3hyphen;mgr; fluorescence intensity on laser power suggests that excitation of the fluorescing states is achieved through a combination of multiphoton absorption and collision processes.
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