Solvated NH₅⁺ formed within ionized clusters of ammonia and ammonia-benzene

"Intramolecular" ion-molecule reactions follow electron impact ionization of neat cluster beams of ammonia and heteroclusters of ammonia-benzene. The resulting fragmentation patterns suggest extensive intramolecular rearrangements occurring within the excited, solvated cation. In addition to the "normal" protonation reaction yielding NH₄⁺ (NH₃)_m ions, a new reaction occurs (only for _m ≳ 4 clusters) forming a series of ions with m/z corresponding to solvated NH₅⁺ cations (similarly for the ND₃ system). The relative yield of the NH₅⁺(NH₃)_m ion product is much enhanced for a heterocluster beam of ammonia with benzene. This is rationalized on the basis of more efficient stabilization of the NH₃-solvated NH₅⁺ by the benzene solvent molecules.