Guided ion beam investigation of the reaction CO++CO:: C-O bond activation and C-C bond formation

We have investigated six different endothermic channels in the reaction of CO+ ions with neutral CO. For each ionic product we have measured the kinetic energy dependence of the integral cross section and inferred the neutral products by the reaction energetics. The onset of the process producing C+, O, and CO, has been identified by a feature of the integral cross section located at about 8.5 eV. Measurements of the product isotopic ratio suggest that C+ originates from both the CO+ ion and the neutral CO molecule. For the reaction channels producing C-2(+)+O-2 and C2O++O, respectively, measurements of the reaction thresholds allow us to estimate the heats of formation of these two ionic products, Delta(f)H(0)(C-2(+))=19.8 +/- 0.2 eV and Delta(f)H(0)(C2O+)=14.7 +/- 0.2 eV. These values are in good agreement with recent independent estimations. Finally, we re-evaluated the dissociation energy of C-2(+)(X (4)Sigma(g)(-)), D-0(C+-C)=6.2 +/- 0.2 eV. (C) 1999 American Institute of Physics. [S0021-9606(99)01343-4].