Comparison of Experimental and Theoretical Vibrational Relaxation Times for Diatomic Gases

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Abstract
A comparison of theoretical and experimental vibrational relaxation times has been carried out for the halogens, nitrogen, oxygen and carbon monoxide. Reasonably good agreement is obtained for all gases except oxygen. For oxygen the predicted variation of the vibrational collision number with temperature appears to be correct; however, experimental values at high temperatures appear to be low by a factor of 0.55. Values obtained at room temperature on the other hand agree well with theory. It would seem therefore that an anomalous decrease in the vibrational collision number takes place in the temperature range from 300° to 500°K. Since data for carbon monoxide could be fitted very well by theory, it is apparent that the effect of radiation is negligible, at least in the temperature range above 1000°K. This is consistent with the value of 0.03 sec for the radiative lifetime of carbon monoxide in the first excited vibrational state. An empirical relationship is established between the interaction constant α and the molecular diameter σ, which reproduces the experimentally derived values quite closely.

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