Origin of Clusters. I. Correlation of Low Temperature Fast Atom Bombardment Mass Spectra with the Phase Diagram of NaCl—Water Solutions

Abstract

Correlations between the structure of samples of the frozen solutions of sodium chloride in water, produced at different parameters of the phase diagram of this system, and the clusters pattern of the corresponding low temperature fast atom bombardment mass spectra are established. Using a model of the independent sputtering of ions from chemically different surface domains, it was concluded that the origin of different types of clusters from different phases of the heterogeneous samples was: (H₂O) _n H⁺—from ice; (NaCl) _m •Na⁺—from anhydrous NaCl; (H₂O) _n •Na⁺, (H₂O) _n •(NaCl) _m •Na⁺, (NaCl)_m•Na⁺—from the crystalline hydrate NaCl•2H₂O. During the thawing of the samples two subsequent phase transitions with increasing temperature were observed, these are sublimation of ice and dehydration of the crystalline hydrate. The differences in the sputtering of (H₂O) _n •Na⁺ clusters from the crystalline hydrate and ice crystals with Na⁺ ion adsorbed on their surfaces are discussed.