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Abstract: Reactions of the hydrocarbon dication C4H3 2+ with a series of atomic and molecular targets (Kr, Xe, N2, NO, NH3, C2H2, and CH4) were investigated in crossed-beam scattering and guided-beam (quadrupole–octopole–quadrupole, QOQ) experiments. Non-dissociative charge transfer (NDCT), leading to the product ion C4H3 +, and proton transfer (PT), leading to the product ion C4H2 +, were observed. In several systems, however, dissociative charge transfer (DCT) contributed significantly to the formation of the product ion C4H2 +. Full scattering diagrams of the products C4H3 and C4H2 + were obtained for the reaction with acetylene. For the other systems, energy profiles of the products close to the angular maximum were obtained. The hydrocarbon products C4H2 + and C4H3 + were scattered mostly forward, suggesting an impulsive mechanism of their formation at the collision energies investigated; the only exception was proton transfer with H2, where the energy profile of C4H2 + indicated substantial backward scattering and formation of an intermediate. From relative translational energy distributions of the products, conclusions could be made about electronic states of the hydrocarbon cations formed in these reactions. [Copyright &y& Elsevier]