Competition of electron transfer, dissociation, and bond-forming processes in the reaction of the CO2~(2+) dication with neutral CO2

摘要

The bimolecular reactivity of the CO_2~(2+) dication with neutral CO2 is investigated using triple quadrupole and ion-ion coincidence mass spectrometry. Crucial for product analysis is the use of appropriate isotope labelling in the quadrupole experiments in order to distinguish the different reactive pathways. The main reaction corresponds to single-electron transfer from the neutral reagent to the dication, i.e. CO_2~(2+) + CO2 → 2CO~(2+); this process is exothermic by almost 10 eV, if ground state monocations are formed. Interestingly, the results indicate that the CO~(2+) ion formed when the dication accepts an electron dissociates far more readily than the CO~(2+) ion formed from the neutral CO2 molecule. This differentiation of the two CO~(2+) products is rationalized by showing that the population of the key dissociative states of the CO~(2+) monocation will be favoured from the CO2~(2+) dication rather than from neutral CO2. In addition, two bond-forming reactions are observed as minor channels, one of which leads to CO~+ and O_2~+ as ionic products and the other affords a long-lived C2O_3~(2+) dication.