SO₂-Metal Ion Clusters

Abstract

INTEREST in the chemistry of gaseous ion clusters has increased sharply since the discovery¹ of water-cluster ions in the D-region of the ionosphere. Furthermore, the fact that the electrical properties of the atmosphere are partly governed by the presence of small ions, which may undergo clustering reactions with trace constituents of the air, has also stimulated research into the properties and structure of the clusters. But knowledge of the structure of ion clusters is still rudimentary. Kebarle and colleagues² have measured the gas-phase hydration enthalpies of alkali ions and compared the experimental results with calculated potential energies of the corresponding water-cluster ions. These calculations, made on the basis of an electrostatic model adopted from the classical theory of complex ions in solution, showed good agreement with the experimental results only for relative values, but not for absolute energies. Other investigators³ have employed molecular-orbital theory to calculate the energies of hydrated protons and shown that, in the case of H₉O₄, a chain structure is as feasible as a symmetrically branched structure proposed by Eigen⁴.