Resonant Auger decay study of core-excited OCS

The present work aims at characterizing short-lived C1s⁽⁻¹⁾π^*(1) core-excited states of the OCS molecule based on the analysis of the vibrational fine structure and lineshape profiles of the high-resolution resonant Auger decay spectra recorded at the excitation energies along the C1s→π^* resonance in the binding energy region 15–19 eV. Very different behavior in terms of lineshape and resonant enhancement is observed for the , and final states. This is explained by (1) the variation in the C–O bond lengths for the states involved in the electronic relaxation and (2) different contributions in terms of Mulliken population to the molecular orbitals determining the electronic character of the corresponding states. Since the final-state geometries are known from a number of previous experiments and ab initio calculations, the geometry of the C1s⁽⁻¹⁾π^*(1) intermediate states can be predicted in analogy with e.g. the N₂, CO₂ and N₂O molecules.     

Line strength measurements of carbonyl sulfide (OCS) in the 2v3, v1+2v2+v3, and 4v2+v3 bands

To support planetary studies of the Venus atmosphere, we measured line strengths of the 2v₃, v₁+2v₂+v₃, and 4v₂+v₃ bands of the primary isotopologue of carbonyl sulfide (¹⁶O¹²C³²S), 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 2v₃ 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 2v₃, v₁+2v₂+v₃, and 4v₂+v₃ of ¹⁶O¹²C³²S (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.     

On the Reaction Mechanism of Br2 with OCS

The reaction mechanism of photochemical reaction between Br2 (^1∑) and OCS (^1∑) is predicted by means of theoretical methods. The calculated results indicate that the direct addition of Br2 to the CS bond of OCS molecule is more favorable in energy than the direct addition of Br2 to the CO bond. Furthermore, the intermediate isomer syn-BrC(O)SBr is more stablethe rmodynamically and kinetically than anti-BrC(O)SBr. The original resultant anti-BrC(O)SBr formed in the most favorable reaction channel can easily isomerize into the final product syn-BrC(O)SBr with only 31.72 kJ/mol reaction barrier height. The suggested mechanism is in good agreement with previous experimental study.