MILLIMETER AND SUBMILLIMETER SPECTRUM OF DSSD.

Work at Duke University supported by the U.S. Air Force Office of Scientific Research. $^{1}$ G. Winnewisser, M. Winnewisser and W. Gordy, J. Chem. Phys. 49, 3465 (1968). $^{2}$ G. Winnewisser and P. Helminger, Bull. Am. Phys. Soc. II, Vol. 14, No. 4, 622 (1969).Author Institution: Department of Physics, Duke University; Division of Pure Physics, National Research Council of CanadaThe millimeter and submillimeter wave spectra of DSSD have been measured using a 6 ft free space cell. DSSD is a very slightly asymmetric top molecule ($K = -0.999992$) and its spectrum shows all the features of a $\bot$-type $transition.^{1}$ The outstanding features of this type of rotational spectrum are the strong Q-branch absorption lines. From the assigned millimeter and submillimeter ground state Q-branch transitions of the $D^{32}S^{32}SD$ species, the band centers for the $^{R}Q_{0}, ^{R}Q_{1}$ and $^{R}Q_{2}$ branches are determined to be: $\begin{array}{l} ^{R}Q_{0}: 69 916.42\pm0.3 Mc/sec (2.332 cm^{-1})\\ ^{R}Q_{1}: 209 737.0 \pm 2.0 Mc/sec (6.996 cm^{-1})\\ ^{R}Q_{2}: 349 540.0 \pm 3.0 Mc/sec (11.659 cm^{-1}) \end{array}$ All transitions originating from the $K \neq 0$ levels show the expected K-type splitting. Because of this and the fact that there is only a small difference between the rotational constants (C-B = -0.29 Mc/sec) the Q-branches have a rather complex structure. A simultaneous analysis of the Q-branch positions shows that the centrifugal distortion treatment with correction terms to $P^{6}$ is not quite sufficient to account for the observed spectra. A similar result was obtained for $HSSH.^{2}$ For the $^{R}Q_{0}$ and $^{R}Q_{1}$branches the measurements were extended to the first excited states (torsional vibrational state $v_{t} = 1$ and the S-S bond stretching vibrational state $v_{o} = 1$). The internal rotational splitting of the ground state as well as the excited states is too small to be resolved, which is in agreement with our observations on HSSH