The rotational gas-phase spectrum of trans- and cis-HSSOH at 100Â GHz

We present the first pure rotational spectra of the two most stable conformers of oxatrisulfane, trans- and cis-HSSOH, in their vibrational ground state. For both conformers a-, b-, and c-type transitions have been recorded in the range from 75 to 120 GHz using an all solid-state spectrometer. More than 200 lines have been assigned for each conformer, most of them belonging to the rQ2- and the rQ3-branch of the perpendicular spectra. The least-squares fit analysis using a semirigid rotor Hamiltonian in S-reduction yields precise values for the ground-state rotational constants A0=21145.93422(66),B0=4479.92301(21),C0=3828.34269(21) for cis-HSSOH, and A0=21071.08204(75),B0=4490.04249(34),C0=3833.20651(35) for trans-HSSOH as well as centrifugal distortion parameters of quartic and sextic order. The ratio of the permanent dipole moment components μb/μc=0.29(3) for cis-HSSOH and μb/μc=0.99(3) for trans-HSSOH has been derived from measured line intensities. All experimentally derived molecular parameters are in very good agreement with high-level quantum-chemical calculations using coupled-cluster techniques, thus confirming the current understanding of the structure of oxasulfanes.