Secondary cluster ion distributions produced by MeV ion impacts on Group IIA oxides and nitrates
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Cluster ion distributions from MeV atomic ion impacts (fission fragments from 252Cf on divalent Group IIA (GIIA) oxides and nitrates have been examined. The two predominant positive cluster species observed from both solids, (MO)nH+ and (MO)nM+ (M denotes metal atom) are evidence of a localized plasma state thought to be created by discrete MeV ion impacts. Cluster intensities and extent of clustering from nitrates were generally greater than those from oxides. The enhanced abundances at certain "magic numbers" of n observed in the mass spectra are believed to arise during the actual cluster production process. These periodic enhancements in cluster stabilities are attributed to the adoption by size-specific clusters of atomic arrangements analogous to segments of the rock salt lattice of the GIIA oxides. Cluster stabilities for the GIIA oxides and nitrates are influenced by the ionicity of M-O bonds, formal valence of metal and radius of cation. Copyright 1996 Elsevier Science B.V. All rights reserved.