Abstract

This thesis presents experimental studies, based on guided ion beam mass spectrometric techniques and coupled to theoretical interpretations by quantum chemistry, on ionic mechanisms for the molecular growth of aromatic hydrocarbons with a particular relevance for understanding the formation of large molecules in ionized gases such as planetary iono-spheres, plasmas and combustion systems. The starting point of this dissertation is a study of the reactivity of naphthyl cation C10H7+ with benzene. Ion-molecule reactions leading to hydrocarbon growth via the formation of new C-C bond are studied with special reference to the association product C16H13+. Another experiment in this dissertation concerns the reactivity of the C12H9+ ion with benzene. The growth of hydrocarbon ions up to C18H15+ species via C–C bond forming reactions is observed. The adduct formation route is found to be exothermic and barrierless, while other products are found to have energy barriers. The last topic addressed in this thesis is the experimental investigation of the possible formation mechanisms of the ion C12H10O+, observed in benzene/air plasma corona discharges at atmospheric pressure.