Three-body dissociation of OCS³⁺: Separating sequential and concerted pathways

Events from the sequential and concerted modes of the fragmentation of OCS³⁺ that result in coincident detection of fragments C⁺, O⁺, and S⁺ have been separated using a newly proposed representation. An ion beam of 1.8 MeV Xe⁹⁺ is used to make the triply charged molecular ion, with the fragments being detected by a recoil ion momentum spectrometer. By separating events belonging exclusively to the sequential mode of breakup, the electronic states of the intermediate molecular ion (CO²⁺ or CS²⁺) involved are determined, and from the kinetic energy release spectra, it is shown that the low lying excited states of the parent OCS³⁺ are responsible for this mechanism. An estimate of branching ratios of events coming from sequential versus concerted mode is presented.