Infrared Dispersion of Carbon Tetrafluoride

The refractive index of carbon tetrafluoride was measured in the 1–20 μ region of the spectrum. The contributions of the molecular vibrations to the index have been calculated and the absolute intensities of the infrared active fundamentals obtained. These are: $$\begin{array}{c}{A}_3{\text{=(1.60±0.01)×10}}^{14}\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}/\sec .\\ A_4{\text{=(1.86±0.13)×10}}^{12}\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}/\sec .\end{array}$$ The results have been interpreted with the aid of a Urey‐Bradley type potential to yield alternate solutions for the dipole moment (μ) of the C–F bond in the molecule and the variation of the moment with inter‐nuclear distance dμ/dr. The calculated solutions are: $$\text{dμ/dr=5.99d/A\hspace{0.17em}\hspace{0.17em}dμ/dr=3.71d/A,}$$ or $$\text{μ=1.13d\hspace{0.17em}\hspace{0.17em}μ=2.98d.}$$ The contributions of the infrared bands satisfactorily account for the difference between the static dielectric constant and the square of the refractive index extrapolated to zero frequency from the visible.