Electronic properties and photofragmentation mechanisms of pyrosulfuryl chloride, ClSO2OSO2Cl

• The first twelve ionizations of ClSO2OSO2Cl arise from Cl and O non-bonding electrons.
• Fragmentation of ClSO2OSO2Cl+ leads mainly to ClSO2OSO2+ and chlorine radical.
• Fragmentation channels of ClSO2OSO2Cl2+ are independent of incident radiation energy.
• Fragmentation mechanisms of ClSO2OSO2Cl2+ start from the rupture of ClS or OS bonds.

The first ionization potential of ClSO2OSO2Cl, was determined by photoelectron spectroscopy at 12.25 eV. The photoelectron spectrum was interpreted, with the aid of DFT calculations, as composed by twelve ionizations of non-bonding electrons localized on the oxygen and chlorine atoms. Several resonant transitions of inner electrons to LUMOs were detected in the Total Ion Yield spectra taken with tuneable synchrotron radiation. Photofragmentation mechanisms of pyrosulfuryl chloride after single and double ionization were studied by means of coincidence techniques (PEPICO, Photoelectron-Photoion-Coincidence and PEPIPICO, Photoelectron-Photoion-Photoion-Coincidence). The main fragmentation mechanism in the valence energy region leads to the formation of ClSO2OSO2+ fragment and a chlorine radical. Other fragments, like ClSO2+, SO2+, ClO+ (arising from an atomic rearrangement) and SO3+ were observed to appear as the energy of the synchrotron light increases. The fragmentation channels after double ionization processes were inferred from the comparison of the shapes and experimental slopes of the coincidence islands for two ionic fragments originating from the same molecule in the PEPIPICO spectra, with the theoretical slopes calculated by the Eland’s formalism. The mechanisms were independent of the incident radiation energy, revealing the lack of site-specific processes. All mechanisms were proposed to start from the rupture of either Cl−S or O−S single bonds for a species which comprises and originates a number of relevant environmental and atmospheric processes and photoevolutions.

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