Knowledge Bank

The torsional-rotational spectra of $CH2DSH$ and $CHD2SH$ have been studied from 12.4 to 50.0 GHz. For the symmetric (trans) configuration, rigid rotor n- and b-dipole transitions have been assigned. For the two asymmetric (gauche) configurations a-, b- and c-dipole lines have been assigned. In this case, the a-dipole lines show a small doubling and are nearly rigid rotor; the b-dipole lines have a large doubling due to internal angular momentum mixing the two asymmetric states and the second order contribution to the rotational coefficient A from the internal angular momentum; and the c-dipole lines are doubled to an even greater extent from the tunnelling between the even and odd states of the asymmetric configurations. Empirical spectroscopic constants will be presented along with the results of the internal rotation-rotation interaction based upon the molecular structure and the internal rotation potential energy.