Electron Attachment to (H ₂O) ₂Ar _n Clusters

The neutral and negatively charged (H ₂O) ₂Ar _n, n = 1-14, clusters are investigated theoretically by use of a polarizable model potential together, in the case of the anionic clusters, with a Drude-model approach to incorporate dispersion interactions between the excess electron and the argon atoms and water molecules. The (H ₂O) ₂Ar ₁₁ and (H ₂O) ₂ ^-Ar ₁₂ clusters are predicted to be "magic numbers", with their high stability being a result of their global minima adopting icosahedral-like structures. On the basis of these results, a mechanism for formation of the anions is proposed. In addition, the rapid falloff in intensity of the n ≥ 7 anionic clusters in the observed mass spectrum and the absence of observable signal for the n = 10 cluster are accounted for.