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

Abstract

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).

Observation of the Carbon Elimination Channel in Vacuum Ultraviolet Photodissociation of OCS

“…As shown on the left of Figure , the time-sliced ion images of the C­( 3 P J= 0 ) products were recorded at six VUV photolysis wavelengths, i.e., 138.53, 135.84, 134.57, 129.32, 128.14, and 126.08 nm, which correspond to the excitations of the parent OCS molecule to a series of vibrational states in the F and P Rydberg states . At all six photolysis wavelengths, well-resolved concentric rings with different intensities are clearly observed in the experimental images, which can be directly attributed to different vibrational states of the SO­(X 3 Σ – ) coproducts.…”

Simulated Electronic Absorption Spectra of Sulfur-Containing Molecules Present in Earth’s Atmosphere

“…In Figure , we present the calculated spectrum of OCS and compare this to the experimental spectrum, which is a composite from Molina et al (4.1–4.8 eV) and Limão-Vieira et al (4.8–9.3 eV). Our calculated spectrum includes the 18 lowest energy electronic excited states for OCS.…”

“…Calculated electronic absorption spectrum of OCS compared to the experimental spectrum from Molina et al (4.1–4.8 eV) and Limão-Vieira et al (4.8–9.3 eV). Obtained from EOM-CCSD results using a combination of the aug-cc-pV­(D+d)­Z+3 and aug-cc-pV­(T+d)­Z+3 basis sets, convoluted using a Gaussian function with δ = 0.1 eV.…”

Photodissociation Dynamics of OCS near 150 nm: The S(1SJ=0) and S(3PJ=2,1,0) Product Channels

“…Six wavelengths were chosen from the strongest resonant absorption lines in the highresolution VUV absorption spectrum of OCS. 34 The absorption peaks in this energy region are well-separated in general. Specifically, wavelengths 147.24, 148.94, 150.70, 152.42, 154.41, and 156.48 nm, which were assigned to the transitions to the six lowest nv 1 + v 2 vibrational progression of OCS, were chosen, where v 1 corresponds to the symmetric stretching vibration mode of OCS, and v 2 corresponds to the bending mode.…”

“…The S atom products formed in the VUV dissociation of OCS were detected using the velocity map ion imaging method at a set of photolysis wavelengths. Six wavelengths were chosen from the strongest resonant absorption lines in the high-resolution VUV absorption spectrum of OCS . The absorption peaks in this energy region are well-separated in general.…”