BOND-FORMING REACTIONS OF GAS-PHASE MOLECULAR DICATIONS

We observe a series of novel reactions involving the formation of chemical bonds in a comprehensive study of the reactivity of eight dications, CF2+, CF22+, CF32+, SF42+, SF32+, SF22+, CO22+, and OCS2+, with the neutral collision partners Xe, D-2, O-2, N-2, NO, and CO. The reactions are detected in a crossed beam apparatus at laboratory-frame collision energies between 30 and 50 eV. The mass-selected dication beam interacts with a pulsed beam of the neutral reactant in a collision region and the ionic products are monitored by a time-of-flight mass spectrometer. The major reactions for each system are charge transfer processes. However, reactions involving the formation of new chemical bonds contribute significantly to the ion yield (1-20%) for several of the collision systems studied. Two classes of bond-forming reactions are observed, one involving negative ion transfer to the dication and the other involving positive ion transfer from the dication to the neutral reactant. An example of the former is the production of DCF2+ from the reaction between CF22+ and D-2; an example of the latter is the production of XeF+ from the reaction between CF22+ and Xe. Estimates of the appropriate curve-crossing radii for the negative ion transfer reactions give values consistent with a Landau-Zener curve-crossing mechanism. Charge transfer products and collision-induced neutral loss channels are also reported in this study.