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SVEN THORWIRTH, GISBERT WINNEWISSER, FRANK LEWEN AND HOLGER S. P. MÜLLER, I. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany; MARKUS BEHNKE, Deparment of Physics, The Ohio State University, Columbus, OH, U.S.A.; JOSEF HAHN, Institut für Anorganische Chemie, Universität zu Köln, 50939 Köln, Germany; JÜRGEN GAUSS, Institut für Physikalische Chemie, Johannes-Gutenberg-Universität Mainz, 55099 Mainz, Germany.
Hydrogenthioperoxide or Oxadisulfane, HSOH, has been uniquely characterized by its recorded millimeter wave spectrum to be a nonplanar molecule with a structure analogous to the two ``parent'' molecules HSSH and HOOH. Because of their near right-angle chain structures, HSOH and the isotopically substituted forms are nearly accidental symmetric tops, but they possess dipole moments essentially perpendicular to the pseudo-symmetry axis. In the case of HSOH, two perpendicular dipole moment components exist, pointing in the direction of the b- and c-axis. This leads to rotational spectra consisting of compact Q-branches and regular, in principle easily discernable P- and R- branches. P-, Q- and R- branches form bandheads in dependence of the quantum number J. For HSOH we have scanned the frequency region of the expected band centers of Ka=1-0, 2-1, 3-2 which occur at frequencies covering the entire frequency region of the Cologne Terahertz spectrometer. These band centers are located at 187 GHz, 561 GHz, and 935 GHz for the rQ0-, rQ1-, and rQ2-branches, respectively.
We will give a demonstration of the complexity of the rQ2-branch at 935 GHz and will present the assignment. The derived preliminary rotational constants are: A=202069 GHz, B=15282 GHz, and C=14840 GHz.