Fragmentation of SO₂ ^q+ (q = 2-4) induced by 1 keV electron collision

We report an investigation on the fragmentation dynamics of SO₂ ^q+ (q = 2-4) induced by 1 keV electron collision utilizing an ion momentum imaging spectrometer. Six complete Coulomb explosion channels were observed using the time-of-flight correlation map. The kinetic energy release distributions for these channels were obtained and compared with those available in the literature. The fragmentation mechanisms of the three-body dissociation channels were analyzed by the Dalitz plots and Newton diagrams. Both concerted breakup and sequential fragmentation pathways were identified in the channel SO₂ ³⁺ → O⁺ + O⁺ + S⁺, whereas only the concerted breakup mechanism was confirmed for the channels SO₂ ⁴⁺ → O⁺ + O⁺ + S²⁺ and SO₂ ⁴⁺ → O²⁺ + O⁺ + S⁺. Using the Coulomb explosion model, we determined the molecular geometry from the concerted fragmentation channels, and the obtained bond lengths and angles from the higher kinetic energy release peaks are close to that of the neutral SO₂ obtained by high-level quantum chemical calculation. The present results indicate that the electron impact experiment is a potential tool for the Coulomb explosion imaging of small molecules.