INFRARED ABSORPTION INTENSITIES AND BOND MOMENTS IN $BF_{3}$ AND RELATED $MOLECULES^{*}$

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 Title: INFRARED ABSORPTION INTENSITIES AND BOND MOMENTS IN $BF_{3}$ AND RELATED $MOLECULES^{*}$ Creators: McKean, D. C. Issue Date: 1955 Publisher: Ohio State University Abstract: The infrared absorption intensities of the fundamental vibration bands of $BF_{3}$ have been measured and vibrational bond moments $\mu$ and their derivatives $\delta\mu/\delta r$ determined. In the $A_{2}^{\prime\prime}$ class, $\mu_{BF} = 1.7 D$; in the $E^{\prime}$ class, $\mu_{BF} = 0.9$ or $2.6 D, \delta\mu/\delta{r} = -6.1$ or $+4.0 D/A$. Inspection of the form of the bending modes suggests that deviations from the bond moment approximation occur such that $\mu(A_{2}^{\prime\prime}) < \mu$ (static) $<\mu (E^{\prime}$). The solution $\mu (E^{\prime}) = 2.6 D$ is therefore preferred. Re-examination of the data of Schatz and Hornig on $CF_{4}$, $SiF_{4}$, and $SF_{6}$ in the light of the present results shows that the vibrational bond moments in these molecules are: $\mu_{CF} = 2.4, \mu_{SiF} = 3.3, \mu_{SF} = 2.7 D$. These moments are roughly equal to $\Delta r_{0}$, where $r_{0}$ is the bond length and $\Delta$ the electro-negativity difference between the atoms in the bond. The magnitudes of the static bond moments in these molecules remain uncertain. Description: Author Institution: Metcalf Chemical Laboratiories, Brown University URI: http://hdl.handle.net/1811/7402 Other Identifiers: 1955-K-4