Laser Induced Combination Band Fluorescence in Ethylene Gas

Laser induced vibrational fluorescence decay measurements have been made for the (v7+v8) and (v6+v10) combination bands of C2H4 gas. The rate of vibration-translation/rotation energy transfer in ethylene was found to be 7.23± 0.3 msec−1·torr−1. This result is in agreement with one sound absorption study but disagrees with several ultrasonic dispersion studies. The rate constants for deactivation of C2H4 during collisions with CH4 and C2H6 were also determined as 8.0 msec−1·torr−1 and 92.0 msec−1·torr−1, respectively. The efficiency of ethane as a collision partner is almost certainly an indication of near resonant vibrational energy transfer between the C2H4 and C2H6 molecules. The dependence of the 5-μ and 3-μ fluorescence intensity on laser power suggests that excitation of the fluorescing states is achieved through a combination of multiphoton absorption and collision processes.