ABSOLUTE INFRARED INTENSITIES OF LINEAR TRIATOMIC MOLECULES IN THE GAS AND SOLID $PHASES^{*}$

Abstract

“The absolute intensities of the infrared-active fundamental vibrations of $CS_{2},\;CO_{2},\;COS$, and $N_{2}O$ have been measured in a polycrystalline solid film. Intensity measurements were made by absorption, using the interference fringe technique of Hollenberg and $Dows^{1}$ to obtain the index of refraction and path length of the solid film. The intensities in the solid films are then compared with the intensities measured in the gas phase. For several of these molecules the intensity of $\nu_{2}$ in the gas phase has not previously been reported, or it has been measured with, insufficient pressure broadening. We have therefore remeasured the intensity of $\nu_{2}$ for $N_{2}O$ and COS, using the curve-of-growth technique as described for $CO_{2}$ by Kaplan and $Eggers^{2}$. As would be expected from the previous comparisons of intensities measured in different phases, the results in each phase are quite different. There is no indication that the intensity sum rule suggested $earlier^{1}$ has any validity for these molecules. For $CS_{2}$ and COS, the intensities increase in going from the gas phase to the solid, by about the amount predicted for the field, effect, using the elliptical cavity treatment of Kalman and $Decius.^{3}$. However, for $N_{2}O$ and for $CO_{2}$ the experimental results do not agree with such predictions.”