Knowledge Bank

Although several workers have reported the infrared intensity of the strong stretching vibration, $\nu 3$, for $CS2$ measured in the gaseous state, apparently no one has yet measured the weaker bending fundamental, $\nu 2$. We have measured the intensity of this vibration in all three phases, and have measured the absolute intensity of the stretching vibration in the solid state, thus completing the data on that vibration in all three phases, also. The solid state intensities have been measured according to the technique of Hollenberg and $Dows.1$ Some difference has been found for the measured intensity of $\nu 3$ depending upon the nature of the window supporting the polycrystalline film. However the measured intensities of both fundamentals are somewhat greater in the condensed phases that in the gaseous state, suggesting that the intensity changes do not result solely from distortion of the normal coordinates of the molecule in the condensed phases. The observed intensification and frequency shift are approximately in agreement with predictions for a molecule in an ellipsoidal cavity, following Kalman and $Decius.2$