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Electronic excitation of carbonyl sulphide (COS) by high-resolution vacuum ultraviolet photoabsorption and electron-impact spectroscopy in the energy region from 4 to 11 eV
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Resumo(s)
The electronic state spectroscopy of carbonyl sulphide, COS, has been investigated using high resolution vacuum ultraviolet photoabsorption spectroscopy and electron energy loss spectroscopy in the energy range of 4.0-10.8 eV. The spectrum reveals several new features not previously reported in the literature. Vibronic structure has been observed, notably in the low energy absorption dipole forbidden band assigned to the (4π←3π) (1Δ←1Σ+) transition, with a new weak transition assigned to (1Σ-←1Σ+) reported here for the first time. The absolute optical oscillator strengths are determined for ground state to 1Σ+ and 1Π transitions. Based on our recent measurements of differential cross sections for the optically allowed (1Σ+ and 1Π) transitions of COS by electron impact, the optical oscillator strength f0 value and integral cross sections (ICSs) are derived by applying a generalized oscillator strength analysis. Subsequently, ICSs predicted by the scaling are confirmed down to 60 eV in the intermediate energy region. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of carbonyl sulphide in the upper stratosphere (20-50 km).
Descrição
F.F.S. and D.A. acknowledge post-doctoral Grant Nos. SFRH/BPD/68979/2010 and SFRH/BPD/99261/2013, respectively, and together with P.L.V. partial funding from the research Grant Nos. PEst-OE/FIS/UI0068/2014 and PTDC/FIS-ATO/1832/2012 through the Portuguese Foundation for Science and Technology, FCT-MEC. P.L.V. acknowledges his Visiting Professor positions at The Open University, UK and Sophia University, Tokyo, Japan and together with NJM the support from the British Council for the Portuguese-English joint collaboration. The authors wish to acknowledge the beam time at the ISA synchrotron at University of Aarhus, Denmark. We also acknowledge the financial support provided by the I3 Integrated Activity on Synchrotron and Free Electron Laser Science (IA-SFS), Contract No. RII3-CT-2004-506008, under the Research Infrastructure Action of the FP6 EC programme Structuring the European Research Area.
Palavras-chave
SCATTERING CROSS-SECTIONS VUV PHOTOABSORPTION SYNCHROTRON-RADIATION OSCILLATOR-STRENGTHS OCS VALENCE HELIUM ATMOSPHERE COLLISIONS General Physics and Astronomy Physical and Theoretical Chemistry