Novel size-dependent chemistry within ionized van der Waals clusters of 1,1-difluoroethane

We present in this paper evidence for size-dependent cluster chemistry occurring in van der Waals clusters of 1,1-difluoroethane. Clusters of C₂H₄F₂ are produced from a neat adiabatic expansion and are ionized via electron impact. In addition to the anticipated fragment ions, we observe ions with the general empirical formula of M_nH⁺ (where n ≥ 4). The reactive process that generates this species cannot be rationalized in terms of intramolecular analogues of known gas-phase bimolecular ion-molecular reactions. Hence, we feel the production of this product cluster ion represents an additional example of a brand new class of ion-molecule reactions that can only occur within the unique "solvated" environment of the cluster.