A multimass velocity-map and covariance-map imaging study of the dissociative electron ionisation dynamics of carbonyl sulphide (OCS)

We present the results of a velocity-map imaging study into the dissociative electron ionisation dynamics of OCS at electron energies of 50, 75, and 100 eV, supported by new equation-of-motion coupled cluster and complete active space self consistent field (CASSCF) potential energy surface (PES) calculations for the OCS⁺ cation and OCS²⁺ dication. We report partial ionisation cross-sections and scattering distributions for the observed ionic fragments, and interpret these in terms of the dissociation dynamics of the singly and doubly charged OCS parent ions formed in the electron–molecule collisions. For many of the dissociation channels, consideration of the calculated PESs supplemented by comparison with data from photoionisation studies provides insight into the electronic PESs involved. For fragmentation products arising from dissociation of the dication, time-of-flight and recoil-frame covariance maps provide mechanistic insight into the stepwise dissociation mechanisms leading to these products and support previous conclusions by other authors.