Line strength measurements of carbonyl sulfide ( 16O 12C 32S) in the 2 v3, v1+2 v2+ v3, and 4 v2+ v3 bands

Abstract

To support planetary studies of the Venus atmosphere, we measured line strengths of the 2 v 3, v 1+2 v 2+ v 3, and 4 v 2+ v 3 bands of the primary isotopologue of carbonyl sulfide ( 16O 12C 32S), whose band centers are located at 4101.387, 3937.427, and 4141.212 cm −1, respectively. For this, infrared absorption spectra in normal carbonyl sulfide (OCS) sample gas were recorded at an unapodized resolution of 0.0033 cm −1 at ambient room temperatures using a Bruker Fourier transform spectrometer (FTS) at the Jet Propulsion Laboratory. The FTS instrumental line shape (ILS) function was investigated, which revealed no significant instrumental line broadening or distortions. Various custom-made short cells and a multi-pass White cell were employed to achieve optical densities sufficient to observe the strong 2 v 3 and the weaker bands in the region. Gas sample impurities and the isotopic abundances were determined from mass spectrum analysis. Line strengths were retrieved spectrum by spectrum using a non-linear curve fitting algorithm adopting a standard Voigt line profile, from which Herman–Wallis factors were derived for the three bands. The band strengths of 2 v 3, v 1+2 v 2+ v 3, and 4 v 2+ v 3 of 16O 12C 32S (normalized at 100% of isotopologue) are observed to be 6.315(13)×10 −19, 1.570(2)×10 −20, and 7.949(20)×10 −21 cm −1/molecule cm −2, respectively, at 296 K. These results are compared with earlier measurements and the HITRAN 2004 database.