Guided ion beam studies of the reactions of Fe+ and Co+ with CS2 and COS

The reactions of Fe+ and Co+ with CS2 and COS are studied using guided-ion beam mass spectrometry: Dominant products in all four systems are MS+ and M CX+ (X = S, O). Cross sections for forming FeCS+ and COCS+ in the CS2 syste ms exhibit two endothermic features, which are assigned to the formation of different structural isomers. From the thresholds associated with forming CoS+ and CoCS+, we determine Do(Co+-S) = 2.95 +/- 0.09 eV and D-0(Co+-CS) = 2.68 +/- 0.34 eV. These values are compared with D-0(Fe+-S) = 3.08 +/- 0.0 4 eV and D-0(Fe+-CS) = 2.40 +/- 0.12 eV determined previously, and the diff erences are discussed in some detail. The results for both metal ions react ing with CXS (X = S, O) suggest that the initial step is predominantly inse rtion of the metal ion into the C-S bond, with activation of the stronger C -O bond being less likely. Comparison of the energy-dependent cross section s indicates that both the CS2 and COS systems show kinetic restrictions for Fe+, which do not occur with Co+. This difference can be attributed to cha nges of spin multiplicities in the various reactions, processes that are di scussed in detail.