SOME EFFECTS OF VIBRATION AND MOLECULAR STRUCTURE ON INTERNAL ROTATION IN $CH_{2}DSH$ AND $CHD_{2}SH$
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Date
1970
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Ohio State University
Abstract
The $J=1\leftarrow(1, \Delta K=U$ and some $J=2\leftarrow 1, \Delta K=0$ lines have been assigned in the microwave rotational spectrum for the partially deuterated methyl mercaptans. The fine structure of the transition, a triplet for each torsional state, has been analyzed on the basis of internal roation and molecular structure. The relative splitting of the triplet cannot be accounted for on the basis of a molecular model with one degree of internal freedom. An effective potential energy term, $V_{1}$ $\cos\alpha$, which orginates in the $\alpha$-dependence of the zero point energy from other vibrations and a Coriolis coupling term with $\cos\alpha P_{\alpha}^{2}$ dependence are introduced to account for the behavior of the torsional substates. Although it is not possible to provide values for each parameter uniquely, limits $1.5 cm^{-1}$ $\leq$ $V_{1}$ $\leq 10 cm^{-1}$ are obtained if only the zero point energy is used. From the splittings, it is possible to determine an improved value of $3^\circ 5^{1}$ for the so-called $C-S$ tilt with respect to the axis of internal rotation. The staggered configuration for the thiol-methyl orientation is found to have minimum potential energy.
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Author Institution: Physics Department, Texas Technological University