Origin of Clusters. II. Distinction of Two Different Processes of Formation of Mixed Metal/Water Clusters under Low-Temperature Fast Atom Bombardment

The preparation of frozen samples, in which the heterogeneous structures differ on a scale comparable to the dimensions of the zone excited by a single bombarding particle, has permitted two different processes of formation of mixed metal/water clusters under fast atom bombardment conditions to be distinguished. Sandwich-like structures, in which sodium ions were located either above or beneath a thin layer of ice, produced different (H₂O) _n •Na⁺ cluster patterns. The formation of only the monohydrate (n = 1) in the first case was attributed to a direct sputtering process, while the appearance of clusters with n ≤ 6 in the second case was connected with the interactions in the deeper regions of the excited zone. Possible differences in desolvation of clusters, dependent on the depth of their origin, were also noted.