VIBRATION-TORSION-ROTATION INTERACTIONS IN MOLECULES WITH A C3v TOP AND Cs FRAME: vt=3,4 TORSIONAL AND C–S STRETCHING VIBRATIONAL STATES OF METHYL MERCAPTAN CH3SH

We present\footnote{This work was done under support of the Volkswagen foundation. The assistance of Science and Technology Center in Ukraine is acknowledged (STCU partner project P686). The work in K{\"o}ln was supported by the Deutsche Forschungsgemeinschaft (DFG) via SFB~956, project B3, and the Ger{\"a}tezentrum Cologne Terahertz Center.} the results of our analysis of the FIR and microwave spectra of the \nub{8} vibrational state (C-S stretch) of methyl mercaptan \chem{CH_3SH} near 710 \wn. The analysis employs a new program which was recently developed for fitting several isolated small-amplitude fundamentals embedded in a pure torsional bath in molecules like methyl mercaptan, in which the frame has C$_{s}$ symmetry and the methyl top has C$_{3v}$ symmetry. Our study involves the energy levels that belong to the \nub{8} vibrational state itself as well as to v$_t$ = 0, 1, 2, 3, 4 torsional vibrational states of methyl mercaptan. In our analysis we used data available in the literature [1,2,3] as well as the results of the new measurements from Kharkiv, K{\"o}ln, and Braunschweig. In the talk the details of this new study will be discussed. [1] L.-H. Xu, R. M. Lees, G. T. Crabbe, et al., J. Chem. Phys. 137, 104313 (2012). [2] R.M. Lees, Li-Hong Xu, B.E. Billinghurst, J. Mol. Spectrosc. 352, 30-38 (2016). [3] R.M. Lees, Li-Hong Xu, B.E. Billinghurst, J. Mol. Spectrosc. 319, 45-56 (2018)