Magnetic properties of sulfur-containing molecules: rotational Zeeman effect and quantum chemical investigation of sulfine, CH2SO, and difluorothiocarbonyl, F2CS, and a new MWFT set-up for on-line pyrolysis studies

Abstract The experimental set-up of a waveguide microwave Fourier transform (MWFT) flow spectrometer for on-line pyrolysis studies is described. Its performance is demonstrated by the rotational Zeeman effect study of difluorothiocarbonyl, F 2 CS. From a fit to the Zeeman splittings the non-zero elements of the molecular g -tensor and anisotropies of the magnetic susceptibility tensor were determined to be: g aa = −0.08672(39), g bb = −0.03690(6), g cc = −0.01981(6); 2· ξ aa − ξ bb = 2.43(21) erg G −2 mol −1 , 2· ξ bb − ξ cc − ξ aa = 8.23(16) erg G −2 mol −1 . Also reported are the results of a rotational Zeeman effect study of sulfine, CH 2 SO, by means of standard continuous microwave spectroscopy. Here the diagnonal elements of the g -tensor and the susceptibility anisotropies were determined to be g aa = −0.34387(15), g bb = −0.09706(3), g cc = −0.05488(3); 2· ξ aa − ξ bb − ξ cc = −0.85(12) erg G −2 mol −1 , 2· ξ bb − ξ cc − ξ aa = 8.78(7) erg G −2 mol −1 . These experimental data were used to derive the diagnonal elements of the molecular electric quadrupole moment tensor and the anisotropies in the second electronic moments for both molecules. In addition, ab initio calculations aiming at the electronic ground state were carried out and the results were compared with the experimental findings. Finally, ab initio values for the 19 F spin-rotation coupling constants of F 2 CS and for the 33 S nuclear magnetic shielding constants are presented; these were calculated via the LORG method using moderately sized basis sets. For sulfine, the reliability of these data was further checked by SOLO calculations.