S−S− velocity images of dissociative electron attachment to OCS

• S−S− ions are produced in dissociative electron attachment e−e− + OCS → CO + S−S−.
• Trimodal speed distributions of S−S− ions are observed.
• Complicated populations of the rovibrational states of CO lead to the specific angular distributions of S−S− ion.

Dissociative electron attachments to OCS with the attachment energies of 4.3, 4.7, 5.0, 6.2, 6.5, 6.8, and 7.0 eV are investigated by measuring the S−S− momentum distributions with time-sliced anion velocity image mapping technique. In this energy range, the ground-state fragmentation, e−e− + OCS → CO(X˜1Σ+) + S−S−(2Pu), is only one dissociation pathway allowed in energy. All velocity images show the predominant feature of the low-speed S−S− ions, but the middle- and high-speed S−S− ions appear at the higher attachment energies (6.2–7.0 eV). The trimodel speed distribution of S−S− ion should be attributed to the different populations of the rovibrational states of CO fragment, however, the dynamic details of above dissociations are still unclear and demand theoretical calculations.

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