The submillimeter-wave spectrum of F₂SO (X∼¹A′)

The sub-millimeter/THz spectrum of thionyl fluoride, F₂SO (X∼¹A′), has been recorded for the first time using direct absorption techniques in the frequency range 286–508 GHz. This work considerably expands the previous measurements for F₂SO, which were all below 77 GHz. F₂SO was synthesized in the gas phase by the reaction of pure SF₆ with residual H₂O vapor either in a DC discharge or a heated reaction chamber. Over two-hundred fifty transitions frequencies were recorded for this molecule in the range J = 16 to J = 30, with K_c = 0–28, each with a c-type pattern. The data were analyzed with an asymmetric top Hamiltonian in a combined fit with previous microwave measurements, and highly accurate rotational and centrifugal distortion constants were determined, including sextic distortion terms that were previously undefined. These parameters are the most accurate set of spectroscopic constants to date for F₂SO. An r_m ⁽¹⁾ structure was determined for F₂SO, which appears to show less steric hindrance than its chlorine analog, Cl₂SO. F₂SO is an important degradation product of SF₆, and its pure rotational spectrum is of interest for environmental studies.