MEAN AMPLITUDES, ROTATIONAL DISTORTION CONSTANTS, AND SHRINKAGE EFFECTS FOR $CF_{4}$, $CCl_{4}$ AND $CBr_{4}$

Abstract

“Using the potential energy constants obtained in previous investigations in this laboratory, the mean square amplitudes of vibration were obtained for $CF_{4}, CCI_{4}$, and $CBr_{4}$ at $298.16^{\circ} K$ by Cyvin’s secular equation $method.^{1}$ The electron diffraction data (available only for $CCI_{4}$ at $295^{\circ} K $) compare very favorably with present calculated values. The rotational distortion constants have also been calculated for these molecules from the potential energy constants, and the shrinkage effects in the internuclear distances have been determined. The mean square amplitudes in {\AA}$^{2}$ for $CF_{4}, CCI_{4}$, and $CBr_{4}$ are respectively: 0.001876, 0.002484, and 0.002643 for $\sigma_{r} (C-X)$, where $X=F, $CL, or Br; and 0.002936, 0.004636, and 0.005877 for $\sigma_{d} (X\ldots X)$. The $D^{J}$ values for $CF_{4}, CCI_{4}$, and $CBr_{4}$ are respectively 1650, 176.7, and 26.5 c/s. The corresponding $D_{J_{r}}$ values are 1156, 132.9, and 21.1 c/s.”