NOVEL CHARGE-TRANSFER ELECTRON-DETACHMENT REACTION FOR THE PRODUCTIONOF NAPHTHALENE DICATIONS AT THERMAL-ENERGY

The reactions of He+., Ne+., and Ar+. with naphthalene have been studi ed with a selected-ion flow tube at 294 K and 0.35 Torr. The major pro duct in the reaction of He+. occurs at m/z 64, which is attributed to C10H82+. The occurrence of this reaction is in agreement with the appe arance potential for formation of C10H82+ from naphthalene. The effici ency of this apparent ''charge-tranfer electron-detachment' process fo r He+. + C10H8, and its recently reported occurrence for He+. + C60 an d Ne+. + C60, indicates that this novel thermal-energy process can com pete effectively with dissociative charge-transfer channels, even when the latter channels are considerably more exothermic. We argue here t hat fragmentation of the target neutral is impeded by the robust natur e of its cyclic structure and that this favors the loss of a second el ectron to form the observed dication. The observation of formation of C10H82+ from He+. reacting with naphthalene at thermal energies has im plications for the formation of PAH dications in interstellar clouds a nd circumstellar envelopes.