Detectable organosulfur compounds

Abstract

Highly correlated ab initio methods are used for the spectroscopic characterization of ethyl mercaptan (CH3CH232SH, ETSH) and dimethyl sulfide (CH332SCH3, DMS) and various isotopologues considering them on the vibrational ground and excited torsional states. Since both molecules show non-rigid properties, torsional energy barriers and splittings are provided. Equilibrium geometries and equilibrium rotational constants are calculated by means of a composite scheme based on CCSD(T) calculations that accounts for the extrapolation to the complete basis set (CBS) limit and core-correlation effects. The ground and excited states rotational constants are then determined using vibrational corrections obtained from CCSD/cc-pVTZ force-field calculations, which are also employed to determine anharmonic frequencies for all vibrational modes. CCSD(T) and CCSD force fields are employed to predict quartic and sextic centrifugal-distortion constants, respectively. Equilibrium rotational constants are also calculated using CCSD(T)-F12.