Knowledge Bank

In this talk we present the first pure rotational lines of Oxatrisulfane, HSSOH. Oxatrisulfane is one link between the well-known skew chain molecules HSSSH and HOOOH. The structure of trisulfane HSSSH has been determined using rotational spectroscopy by Liedke~\textit{et al.}}, {\em J. Mol. Struct.} {\bf 413} 265--270 (1997)} showing HSSSH to form two stable conformers, \textit{trans} and \textit{cis}, with the \textit{trans}-conformer to be slightly more stable. Only recently hydrogen-trioxide HOOOH has been discovered by Suma~\textit{et al.}}, {\em JACS} {\bf 127} 14998--14999 (2005)} observing the rotational spectra of the \textit{trans} conformer. For this molecule no evidence for the \textit{cis} structure has been found. First experimental evidence for the formation of HSSOH was given by Konigshofen~\textit{et al.}}, {\em Z. Anorg. Allg. Chem.} {\bf 625} 1779--1786 (1999)} via flash vacuum pyrolysis of t-BuS(O)St-Bu at T $>$ 700C using IR-spectroscopy to monitor the pyrolysis products. We employed this method to synthesize HSSOH and performed first high-resolution millimeterwave measurements in the range of 75--120~GHz by introducing an all solid state spectrometer. More than 170 lines of the \textit{cis} conformer and more than 30 lines of \textit{trans}-HSSOH have been undoubtly identified. Both conformeres are close to the limiting case of a prolate symmetric top with $\kappa cis=-0.925$ and $\kappa trans=-0.924$ respectively. Their permanent dipole moment points mainly along the \textit{b}- and \textit{c}- principle axes and therefore the spectrum displays a clear perpendicular structure. For analyzing the identified lines a standard \textit{S}-reduced Hamiltonian has been used and we were able to fit the rotational parameters $A$, $B$, $C$ as well as the centrifugal distortion parameters $DJ$, $DJK$, $DK$, $d1$ and $d2$. The \textit{c}-type transitions of \textit{cis}-HSSOH are approx.~14~times more intense than the corresponding \textit{b}-type transitions, whereas in case of \textit{trans}-HSSOH the intensities of the \textit{b}- and \textit{c}-type transitions are almost equal. All experimentally derived parameters are in excellent agreement with those obtained by high level ab initio calculations}.