Microwave spectra of dimethylsulfide- d6, (CD 3) 2S, ground and excited torsional states

Abstract

The microwave spectra of the molecular isotope (CD 3) 2S in the ground state and the first and second excited states of methyl top torsion (internal rotation) and of CSC deformation as well as the ground-state spectra of the 13C and 34S substituted forms have been measured. The rotational constants and centrifugal distortion and rotation-vibration interaction constants could be determined. The rotational lines in the excited torsional states (1 1, 1 2, 2 1, 2 2, 2 3) were found to be split into quartets due to the interaction between molecular rotation and methyl top internal rotation. The experimental multiplet splittings were fitted to those calculated from a rotation-internal rotation Hamiltonian in order to obtain values for the internal rotation barrier V 3 and the top-top interaction potential coefficients V 12 and V′ 12. V 12 was too highly correlated with V 3 for a separate determination. The values following from the least-squares adjustment are discussed.