# Internal rotation in dimethylacetylene

Mills, I. and Thompson, H. W. (1954) Internal rotation in dimethylacetylene. Proceedings of the Royal Society, Series A, 226 (1166). pp. 306-314. ISSN 1471-2946 (online)

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The vibrational spectrum of dimethyl acetylene has been remeasured with better resolving power than hitherto, and the rotational fine structure of some perpendicular type bands has been partly analyzed. The energy levels of a molecule of this kind in which internal rotation of methyl groups may arise have been re-examined theoretically and the rotational structure of the absorption bands has been more clearly defined than previously. The experimental results are consistent with the assumption of unrestricted internal rotation of the methyl groups, and the Coriolis factors $\zeta _{i}$ for several vibrations have been determined.