OCS2+ dication spectroscopy and electronic states

High level electronic structure calculations on the OCS2+ dication made by the spdfg cc-pV5Z/CASSCF/MRCI method are presented. They enable a detailed interpretation of the newly recorded spectra of this ion made by the time-of-flight photoelectron photoetectron coincidence (TOF-PEPECO) method, and provide a reliable basis for analysis of its dissociation pathways. The major dissociation to CO+ + S+ appears to occur not on the ground state surface, but from an excited electronic state. Possible involvement of the CSO2+ isomer in dissociation is discussed. (C) 2007 Elsevier B.V. All rights reserved.