Knowledge Bank

High pressure transmission measurements of $N2,CO2$, and $SF6$ are taken using a BOMEM DA3.02 vacuum spectrometer. A 30.5 cm long cell capable of 68 atm maximum pressure and of temperatures from 295 to 500 K is used in the experiment. The entire optical path is under vacuum. The spectral range covered is from 1800 to $5000cm-1$. Measurements of the integrated intensity on the collision induced absorption (CIA) of the fundamental vibration band of $N2$ are obtained as a function of temperature. Our resuits and $others1,2,3$ are compared to the theory by Van $Kranendonk.4$ An excellent fit is obtained from 77K to 500K. Integrated intensities are also obtained for the $2\nu 1$ and $\nu 2+\nu 3$ CIA bands of pure $CO2$ and mixture with $N2$. These bands are strongly influenced by $N2$. CIA contributions to the intensity of the infrared allowed $3\nu 3$ band was observed and at the highest pressure (21.1 atm), accounted for approximately 50% of the integrated intensity. The CIA contributions fall off rapidly with increasing temperature.