The SOLEIL view on sulfur rich oxides: The S2O bending mode nu(2) at 380 cm(-1) and its analysis using an Automated Spectral Assignment Procedure (ASAP)

The fundamental vibrational bending mode nu(2) of disulfur monoxide, S2O, and the associated hot band 2 nu(2) - nu(2) have been observed at high spectral resolution for the first time at the SOLEIL synchrotron facility using Fourier-transform far-infrared spectroscopy. This transient species has been produced in a radio-frequency discharge by flowing SO2 over elemental sulfur. The spectroscopic analysis has been performed using the newly developed Automated Spectral Assignment Procedure (ASAP) which has enabled the accurate determination of more than 3500 energy levels of the nu(2) = 1 and 2 vibrational states. The procedure provides a fast and convenient way to analyze large data sets in a straightforward manner, if one of the two vibrational states involved in the transition is accurately known from prior work. In addition to the high-resolution synchrotron study, pure rotational spectra of S2O in the nu(2) = 1 and 2 vibrational states were observed in the frequency range 250-500 GHz by absorption spectroscopy in a long-path absorption cell. From these combined measurements, extensive molecular parameter sets have been determined, including full sets of sextic and two octic centrifugal distortion terms. Highly accurate band centers (to better than 10(-5) cm(-1)) have been derived for both vibrational bands. (C) 2015 Elsevier Inc. All rights reserved.