Microwave spectroscopic investigation of thionyl chloride, SOCl2: hyperfine constants and harmonic force field

Abstract

The rotational spectrum of the most abundant isotopomer of thionyl chloride, ³²S¹⁶O³⁵Cl₂, has been recorded in the frequency range 7.8–24.7 GHz using a pulsed molecular-beam microwave spectrometer. 262 lines of 27 rotational transitions (b- and c-type) have been used to determine rotational and quartic centrifugal distortion constants and the complete ³⁵Cl nuclear quadrupole coupling tensor, as well as spin–rotation coupling constants. Whereas the diagonal quadrupole coupling constants in the inertial axis system agree with those from previous microwave studies, disagreement is observed for the principal values χ_zz(–63.8 MHz) and η(–0.0143). However, the value of χ_zz is in good agreement with those derived from solid-state NQR measurements. The centrifugal distortion constants together with vibrational wavenumbers and amplitudes have been used to refine the harmonic force field. The principal quadrupole coupling constants and the force constants are compared with those of related molecules, and the latter have been used to propose a reassignment of two vibrational bands of the related molecule, SO₂Cl₂.