Small Angle X-Ray Scattering from Solutions of Alkali Metals in Liquid Ammonia

Abstract

The small angle x-ray scattering from solutions of lithium, sodium, and potassium in liquid ammonia has been measured using molybdenum K radiation. Scattering curves were obtained for a series of concentrations of lithium solutions at —75°C, for one concentration at —45°C and —75°C, for potassium, sodium, and lithium solutions of approximately the same molarity, and for lithium and sodium solutions near saturation. The scattering data indicate the presence of scattering centers of dimensions of the order of 15 A, with at most a few types of centers in a given solution, and with the type of center depending on the metal ion. There was no evidence for the simultaneous presence of cavities with diameters of the order of 8 A. Calculations indicate these cavities probably would have been observed if present. These results are in good qualitative agreement with the theory of Becker, Lindquist, and Alder. The ``hole theory'' developed by Lipscomb and by Kaplan and Kittel would require modification to account for the observed scattering.