Reactions of cations derived from naphthalene with molecules and atoms of interstellar interest

The chemistry of naphthalene radical cation and its derivatives (C(10)H(n)(+), n = 6,7,8,9) has been studied with molecules and atoms of interstellar interest in a selected ion flow tube. The radical cation C(10)H(8)(+) is unreactive with H(2), CO, H(2)O, and NH(3) but reacts with H, O, and N atoms. Adduct formation is the only channel detected in the case of reaction with H atoms, but additional channels contribute in reactions between C(10)H(8)(+) and O and N atoms; these latter reactions proceed through novel reaction pathways via C and CH abstraction, leading to the formation of the stable compounds CO and HCN, respectively. The closed-shell naphthylium cation C(10)H(7)(+) is essentially unreactive with atoms but associates via nucleophilic addition with most of the molecules studied. The reaction kinetics are close to saturation in the accessible helium pressure range. The naphthyne radical cation C(10)H(6)(+) does not react with H(2), CO, or H(2)O but forms an adduct with NH(3) at a moderate rate. Reactions with atoms were found to be very similar to those of C(10)H(8)(+) The implications of these results for the stability of polycyclic aromatic hydrocarbon cations in the interstellar medium are briefly discussed.