THE ABSOLUTE INTENSITY OF INFRARED ABSORPTION BANDS IN $CH_{2}F_{2}, CH_{2}Cl_{2}, CH_{2}Br_{2}$, AND $CF_{2}Cl_{2}$
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Date
1955
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Ohio State University
Abstract
The absolute intensities of infrared absorption bands of species $B_{1}$ and $B_{2}$ have been determined for the halogenated methanes $CH_{2}F_{2}, CH_{2}Cl_{2}, CH_{2}Br_{2}$, and $CF_{2}Cl_{2}$. For the three methylene halides, the bond moments $\mu_{CH}$ and $\mu_{CX}$ and the bond derivative $\delta{\mu_{CX}}/\delta r_{CX}$ have been determined. The ambiguity in sign of the bond derivative $\delta\mu_{CH}/\delta r_{CH}$ has not been resolved. The bond moments $\mu_{CX}$ are all assumed to be negative; their numerical values vary in a nearly linear manner with the electronegativities of the halogens in question. The bond moments $\mu_{CH}$ are all positive but differ from molecule to molecule being larger in $CH_{2}Br_{2}$ than in $CH_{2}F_{2}$. The sign of the bond derivatives $\delta\mu_{CX}/\delta r_{CX}$ is opposite that of the associated $\mu_{CX}$ and in each case represents an effective charge of approximately 0.7e. The simplified model does not yield consistent results when applied to bands of different species in $CF_{2}Cl_{2}$.
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Author Institution: Department of Physics, University of North Carolina